While foothills of the Taurus Mountains saw the development of the earliest stone temples, furnace-based crafts, permanent settlements, and agriculture, it would be to the south, in the delta region of the Tigris and Euphrates Rivers, where all these technologies and societal developments would coalesce to create the earliest human civilization: Ki-en-gir, “Land of the Lords of Light.” We know it today as Sumer. What really distinguished Sumerian civilization was its written language, which is the true dividing line between prehistory and history. The beginnings of the Sumerian writing system were simple enough. The burgeoning growth of agriculture required enumeration beyond the easy reference of the digits of both hands, so a written transcription of small inventories was first conceptualized as numerical scratches or hash marks under a picture of the item being tallied. This became more complex as more products and services needed to be depicted. Soon, symbols representing specific actions and ideas were added. Eventually, the Sumerians used letters made of wedge groupings called cuneiform (Latin for “wedge shaped”) to represent the different sounds of human speech. A simple reed stylus was used to impress the wedges onto a wet clay tablet that was then baked or left to dry. This phonetic cuneiform script became one of the world's most successful writing systems and was adopted by many of the peoples whose cultures and kingdoms would follow the Sumerians in the Tigris-Euphrates delta. It endured for almost four thousand years, surviving until the second century of the Common Era. Tens of thousands of cuneiform tablets have been uncovered and translated, providing archaeologists and historians with a rich source of information about the everyday lives of the people, both commoners and royals, who trod the earth of ancient Iraq and Syria.
Clay not only formed the basis of the Sumerians' revolutionary writing system; it was also their principal construction material. The river deltas that gave birth to the earliest civilizations were also rich in mud clays. These clays were pressed into a simple rectangular wooden mold and then dumped out to dry in the sun. The clay mud also provided a cheap mortar and plaster. Primitive adobe masonry can create relatively sturdy one-story structures whose thick walls keep the interior cool in summer and retain heat in the winter. If regularly maintained, an adobe structure can last centuries. Adobe remains one of the most popular building materials in many of the warmer climes of the Third World.
The kilning of limestone to produce lime continued: having long lost its seemingly supernatural charms, it was probably looked upon as a fine, but terribly expensive, building material. There was less limestone in the lower Tigris-Euphrates region than in the mountains to the north, and the wood needed to fuel the kilns was also a scarcer resource in the delta. Straw and wood from riparian trees would serve as cooking fuel and for kilns, but the latter were restricted mostly to pottery making, since metal-forging ovens used more efficient charcoal as fuel. Although metal forging required higher temperatures, the smiths needed to concentrate their heat in only one small spot, charged by their bellows, rather than across a large interior space that was the size of a small room. The end of the second millennium BCE saw increased use of kilns to make a new building material: baked bricks. Like pottery, bricks required a shorter bake time and lower temperatures than did lime production. However, because the large number of bricks required for building purposes was substantial, their use was mostly restricted to public buildings or palaces financed by kings. As the grand, conical ziggurats of Babylon rose to the sky, the preferred building materials were cut stone or brick masonry, with adobe used within their thick walls as cheap filler.
It was not only the huge fuel requirements that limited lime's use as a mortar during the Sumerian and later Mesopotamian empires but also the discovery of two other materials that seemed more practical. The first was gypsum, the material now used to make plaster of paris. Just as calcium carbonate is the chief constituent of limestone, so calcium sulfate is the principal element of gypsum. To the ancients, gypsum must have appeared to be a good alternative to limestone. It calcinates at a far lower temperature (120°C / 248°F), and the resulting powder is far less caustic (you can scoop it up with your hands with no ill effects). Add water to the powder, and though the resulting mixture is very warm, it does not generate the scalding temperatures of its chemical cousin. Once thoroughly hydrated, the substance sets after a few hours, returning to its original state as a hard mineral. Gypsum did not create a mortar as hard or adhesive as the lime-based one, but it was probably “good enough” for the ancient contractors, who no doubt appreciated the fact that they did not have to worry much about their sons, apprentices, or themselves being seriously injured while handling the material.
Another useful substance locally abundant was tar, which bubbles up in some spots from the vast subterranean collections of petroleum that lie beneath the crust of this part of the Middle East. Unlike limestone or gypsum, tar requires no processing; it can be used as is. As a result, the petroleum that would one day bring great wealth to the region was initially used as a convenient and satisfactory masonry adhesive.
Lime concrete and mortar did not disappear during the Sumerian, Akkadian, Babylonian, or Hittite Empires of Mesopotamia. In places where trees and limestone remained plentiful, the old white magic continued to be practiced. It was still the best stuff around.
LAND OF THE PHARAOHS
Rich clay deposits surrounded the Egyptians of the Nile Delta as they did the people on the Tigris and Euphrates. Naturally, sun-dried blocks served most of their building needs and would continue to do so for thousands of years.
The exceptions were grand tombs and monuments. From the time of the earliest dynasties, Egyptian rulers wanted to be buried in lavish tombs that would serve their imagined needs in the afterlife. The first of these tombs were mastabas. Mastaba is Arabic for “bench”—an appropriate name for these rectangular structures, the interiors of which replicated the ruler's own domiciles, with the same rooms set aside for various purposes, complete with furniture and artwork. The tomb chamber was hidden underneath the main structure. The earliest mastabas were built of adobe bricks; centuries would pass before the pharaohs switched to the more permanent limestone. Interestingly, the walls of the first limestone mastabas were carved and painted to resemble clay bricks. In other words, the early Egyptian rulers still lived in adobe structures, but, knowing the material's limited life span, they sought a substitute that would endure for the eternity of an afterlife: limestone. Still, it had to resemble the walls of their own palaces and so was made to appear like clay. The mastabas gradually became larger and more elaborate, paralleling the pharaohs' own increasingly opulent lifestyles. Stories (called “steps”), each with sloping walls, were added to the later mastabas. The Egyptian word for mastaba seems to have meant something like “place of ascension.” Evidently, the additional steps meant a higher mastaba, and so the less one would need to ascend.1
When the Third Dynasty pharaoh, Djoser (2667-2648 BCE), came to power, he wanted to build a mastaba grander than those of his predecessors. Work on the structure began early in his reign at a place now called Saqqara, then known to the ancient Egyptians as kbhw-ntrw. (Like all ancient Semites, the Egyptians were somewhat averse to expressing their vowels in writing.) The largest previous mastaba had three steps, so Djoser, of course, wanted four. His architect was the renowned Imhotep, who would be deified centuries later as Egypt's “Father of Architecture, Sculpture and Medicine.”2 (Poor Imhotep would later be vilified in American and British “mummy movies” in which he appears as the resurrected heavy. The plot equivalent would be that of an undead Leonardo da Vinci rising from his tomb to terrorize modern Florence.)
Either Djoser kept changing his mind, or Imhotep kept urging his master to build on a grander scale, for there are three distinct modifications to the tomb. The first version is a typical mastaba, though grander than earlier ones and featuring a fourth step. The structure was then enlarged, and a fifth step was added. Shortly after this phase, all the stops were pulled, and a sixth step was added, as well as a dazzling temple precinct surrounding the pyramid. The temple precinct incorporated not only every architectural form then known to the Egyptians but several others never seen before, which would serve as archetypal designs for Egyptian buildings over the next three thousand years: the first colonnade (using the first fluted columns); the first columned hall, called a “hypostyle”; the first cavetto cornices; the first porticos; the first life-size statues, and, of course, at the center of it all, the first pyramid: the famous step pyramid of Djoser. Instead of just a large burial chamber underneath the pyramid, Imhotep built an underground warren of hallways, tunnels, and shafts that stretch almost four miles in length, connecting some four hundred rooms and galleries. To fool any would-be tomb raiders, much of the underground labyrinth was designed as a series of mazes that led to multiple dead ends and false entrances. (Djoser's mummified remains and treasure would remain safe for a few centuries, but like all the pyramid tombs, it would eventually be found and robbed of all valuables.)
Djoser's six-step pyramid is just above 60 m (ca. 197 ft) high and echoes the older mastabas in that it is rectangular: 173 m by 107 m (ca. 568 ft by 351 ft). Limestone was used to a greater extent here than in all previous Egyptian buildings combined. (One could make a case that the amount of limestone used in Djoser's pyramid and tomb district exceeded all previous human construction efforts with this stone combined) Surrounding the tomb complex was a ten-meter-high (ca. 33 ft) wall that was 1.6 km (1 mile) long made from pure white limestone from Tura, Egypt. The temples inside the district were also built of limestone, and their walls were masterfully carved with depictions of Djoser enjoying such bucolic pursuits as hunting, fishing, and dispatching enemy soldiers with club blows to the head.3 No longer were the walls made to appear like adobe bricks, for by this time pharaohs lived in limestone palaces. Clay bricks were now for the common folk.
Shortly after Djoser's reign, a new family came to power, which we call the Fourth Dynasty. As before, each pharaoh of this new dynasty would compete with his antecedent and build tombs larger and more perfectly proportioned than the previous ones. These remarkable structures would reach their apogee during the reign of the pharaoh Khufu (2589-2566 BCE), who would build the most magnificent of all these monuments, the Great Pyramid of Giza. The finished result rose 147 m (ca. 482 ft), and its four-sided base was a perfect equilateral square, 230 m (ca. 755 ft) per side. The pyramid was built with solid blocks of limestone, with the finest white limestone reserved for its exterior cladding, or overlay. Gypsum4 was used to cover the masonry joints, and the stone was then polished to a smoothness that reflected the sun with an almost mirror-like intensity.5 The best stone—the exterior Tura limestone cladding—was removed centuries later to build palaces and mosques in medieval Cairo. Even with its magnificent exterior stripped away, the Giza pyramid is staggering to behold. Barring multiple nuclear attacks, it will probably outlast any other human-made structure—and probably the human race as well.
But was limestone really used to create the pyramids? The blocks appear to be limestone, but according to two materials engineers, a substantial part of the pyramids—most notably Khufu's Great Pyramid—actually consists of cast concrete. If this is true, the pyramids represent the greatest volume of concrete manufactured and applied to a single engineering project until the construction of the Panama Canal some twenty-four centuries later.
THE GREAT CONCRETE PYRAMID CONTROVERSY
The Egyptian pyramids have always been magnets for people proposing fringe theories—to put it politely—about their creation. Despite the fact that a dozen pharaohs spent over a century perfecting the building techniques required for the construction of the pyramids, some people still cannot believe that the ancient Egyptians built these remarkable monuments without some sort of mysterious assistance. Some suggest that extraterrestrial aliens (their most popular locus being the Pleiades star group) were involved, while others opt for tech-savvy survivors of the “lost continent” of Atlantis. Many respected Egyptian authorities would prefer to term such theories as “unhinged” rather than “fringe”; the latter suggesting that these imaginative scenarios have one foot grounded in truth and the other in speculation. “Unhinged” seems to be the better adjective for describing the alien- or Atlantis-based theories.
Somewhere in the middle ground between the unhinged and the more widely accepted theories about pyramid construction is the cast-concrete-block hypothesis proposed by two men with respectable scientific credentials. Neither Michel W. Barsoum, a professor of materials engineering at Drexel University in Philadelphia, nor chemical engineer Joseph Davidovits, head of the Geopolymer Institute in Saint-Quentin, France, come across as fringe—or unhinged—theorists. Yet these two men have lit the fire of perhaps the most hotly debated controversy in Egyptology today: that major portions of the pyramids were built of concrete, not limestone, as many archaeologists and historians believe.
The Frenchman started it. Davidovits suggested back in the early 1980s that some of the rock he examined at the Great Pyramid looked more like concrete than limestone.6 And not just any concrete: an eco-friendly version using a “geopolymer.” To refresh your memory of high school chemistry, a polymer is a long molecular chain that lends strength and/or stability to a chemical compound. One example of a geopolymer—a natural polymer arising from the earth—is petroleum. (Davidovits has trade-marked the preexisting term, converting it to his proprietary Geopolymer™) According to Davidovits, his Geopolymer concrete—which he claims the Egyptians were the first to discover—uses an alkali solvent, natron (sodium carbonate), in water to dissolve clay rich in aluminosilicates. (Aluminosilicates are the mineral form of aluminum and silicon that are needed to serve as a concrete binder.) Crushed limestone and a little lime is added to this soup, which is then thoroughly mixed and allowed to dry to a thick mud form, during which time the dissolved aluminosilicates recondense to form a stronger crystalline structure. The resulting “mud” is then rammed into wooden forms in a process similar to that used to create adobe bricks—although with far larger molds, of course. The result is a block with a look and texture very similar to stone. A demonstration of the process can be viewed at http://vimeo.com/l657432. (To more clearly make his point, Davidovits dressed his workers in ancient Egyptian garb.)
Davidovits's hypothesis is both ingenious and intriguing. He believes that soft limestone with a high clay content was quarried near the Giza Plateau, then dissolved in a water, lime, and natron solution (natron was used by the Egyptians for mummification) and held in large pools or holding tanks fed by the Nile. The pools were then left to evaporate, leaving behind a moist mud, the ancient equivalent of wet concrete. This concrete was carried to the pyramid site in baskets where it was tamped into molds. After a few days, the concrete would cure, forming a building block for the pyramid. Davidovits claims that a work crew of just ten people could make a dozen large blocks within the span of several days. Since the blocks were cast in place, no elaborate hoisting equipment or levers were needed to build the pyramids. By using their smarts, and not their sweat, the Egyptians saved millions of man-hours in constructing the pyramids. Davidovits explains his theory in detail in a book coauthored with Margie Morris titled The Pyramids: An Enigma Solved.7 His revisionist account of Egyptian engineering is compelling and disturbing. If Davidovits's explanation is accurate, Egyptian history would need to be reevaluated, countless books about Egypt's architectural splendors rewritten, and, of course, numerous History Channel documentaries scrapped, as well. And could anyone ever again watch the Hebrew slaves struggling to build Pharaoh Rameses's monuments in Cecil B. DeMille's The Ten Commandments without shaking their head and muttering disapproving smart-aleck remarks? (Or, at least, more smart-aleck remarks than the film already provokes?)
Putting aside Egyptian building techniques for a moment, the low-lime concrete discovered—or rediscovered—by Davidovits seems to offer great promise. The resulting concrete has great compressive strength and uses only a very small amount of lime and no kilned clay. If we assume that its bugs can be worked out—it is still non-hydraulic and begins to fall apart when immersed in water for more than two weeks—this Geopolymer concrete could substantially cut the energy required for, as well as the pollution generated from, cement manufacturing.
Egyptologists hotly contest Davidovits's theory. They point out that there is no historical data supporting this form of construction and that engineers have already examined the limestone quarries near Giza and calculated that the amount of removed stone was roughly equivalent to that used for all monuments in the area. As for the resemblance—at least to the human eye—of Geopolymer concrete to limestone, even standard concrete resembles a variety of limestone and even some granite.8
There the matter stood until 2004, when Egyptian-born Michel Barsoum took a trip to Khufu's pyramid while visiting his native country. Hiking around the monument, he noticed that a few of the stone blocks looked more like concrete than limestone. Selecting several different blocks, he knocked off a few pieces with a rock pick, put the fragments in a plastic bag, and brought them back to Drexel University to study.9 Barsoum should not have taken samples in this manner, but he knew that applying for official permission would be a long, drawn-out affair. There was also a good chance that his request might be denied. The former minister of state for Egypt's Antiquities Affairs, Zahi Hawass, ruled his fiefdom with an iron fist and was very cautious about granting site permits. (Hawass, who has never been accused of being shy, pops up in seemingly every recent television documentary about ancient Egypt.)
Examining the fragments under a microscope, Barsoum discovered a kind of crystallization commonly found in concrete, but not in limestone. A Columbia State University geologist, David Walker, agreed that the microscopic examination “certainly revealed things you wouldn't expect to find in normal limestone.”10 To Barsoum, this suggested that some twenty-five hundred years before the Romans began using concrete, the Egyptians had been using it on an even more massive scale to construct their pyramids. Unlike Davidovits, Barsoum believes that concrete construction was not used on most of the pyramid's blocks but only the outer portions beneath the limestone sheets covering the structure.
Because of the controversial nature of his findings, Barsoum had trouble getting his paper published in a scientific publication. Eventually it was printed in the December 2006 issue of the Journal of the American Ceramic Society.11 As the journal started reaching subscribers in late November, Barsoum began talking to the media. He also put together a slideshow to explain his work,12 in which he shows microscopic images that contrast the different crystallization of concrete fragments and limestone. Barsoum also points to photographs that show that the pyramid blocks fit together so precisely, a thin sheet of paper cannot be placed between them. This, he contends, typifies cast concrete but would be almost impossible to achieve with stone carved with the relatively soft copper tools that the Egyptians used. A materials science professor at MIT, Linn Hobbs, was intrigued by Barsoum's work and assigned his students the task of building a small-scale pyramid using Geopolymer concrete. The project was completed without any difficultly, demonstrating that the technology was certainly feasible.13
Naturally, Joseph Davidovits was happy to see his original hypothesis apparently vindicated. A masterful and indefatigable publicist, Davidovits churned out a new flurry of press releases, papers, and online videos about his theories, and pointed to Barsoum's data and Hobbs's model pyramid as collaborative evidence.
One cannot help but be impressed by the amount of evidence Davidovits has marshaled in support of his theory. Studied in isolation, the case he presents in his books and papers seems almost unassailable. Unfortunately, almost all the evidence he and Barsoum point to is either misleading, wrong, or very wrong. It is a theory that, while extraordinarily clever, ignores a mountain of conflicting data. There are no limestone deposits rich in clay (called “marl”) near Giza—although it's possible some existed thousands of years ago—and no pools have been uncovered that could have been used to process the concrete. There are no nearby sources of natron14 or any other archaeological evidence that might support Davidovits's hypothesis. Independent scientists have exhaustively tested core samples from the monument stones and compared them to
Davidovits's Geopolymer concrete. They found no similarities.15 Many of the blocks on the pyramid still show, even after the weathering of centuries, clear quarry markings. They are unquestionably limestone—and unquestionably the same limestone found at the quarry near Giza. As for the precisely fitted masonry blocks seen at the Egyptian pyramids, this kind of masterful carving is hardly unique. Mayan and Inca stonecutters in Mesoamerica achieved similar precision using tools more primitive than those of the Egyptians. Finally, it must be remembered that Khufu's tomb chamber within the pyramid is constructed with granite,16 and granite is far harder to carve than limestone, especially with primitive tools. Yet, the Egyptians managed to do so.
What about Barsoum's sample from the Great Pyramid that seems to identify it as artificial stone? It may well be artificial stone, and concrete at that. The Egyptian monuments have been subjected to major restoration projects since pharaonic times and during the Roman period, as well. Concrete blocks were used in the modern era to fill in some gouges left by quarrying performed in medieval times. Zahi Hawass believes that this was the source of Barsoum's fragments: “I would ask Dr. Barsoum the question: where did he get the samples he is working with, and how can he show that the samples are not taken from areas that have been restored in modern times?”17
Barsoum and Davidovits have apparently decided to defend their position by mounting a good offense. Do an Internet search for “concrete pyramids,” and you will get a blizzard of hits that originate from their websites, or from the regular interviews the men grant reporters, or from mainstream media stories that simply recycle their press releases (apparently written by research-averse reporters who simply ask the opposing side for a few brief remarks). It is the cyber version of a debate in which one advocate is soft-spoken while the other uses a megaphone. Unfortunately, Davidovits's refusal to yield on this long-settled controversy is obscuring his exemplary work in developing an eco-friendly concrete that also possesses high compressive strength. The potential energy savings and pollution-curbing attributes of Davidovits's Geopolymer concrete is more vital to the public interest than his attempts to uphold a fascinating but deeply flawed theory on how the pyramids were constructed.
Toward the end of third millennium BCE, a seafaring people from the island of Crete began showing up at ports throughout the Eastern Mediterranean, eagerly looking for items to trade. They had mastered the art of constructing small ships capable of sailing long distances and sturdy enough to carry tons of cargo. This gave them a decisive trading advantage over other peoples who lived on the Levantine coast. These seafarers eventually created a mercantile empire with colonies or trading posts throughout the region.18 We call the people of this lost kingdom the Minoans for the legendary King Minos, who reportedly once ruled the island of Crete.19 In truth, we do not know what they called themselves.
Trading not only brought the Minoans wealth but, more importantly, exposed them to the arts and sciences of the many societies with which they came into contact. These skills and arts were adapted and then refined by the Minoans. By 1700 BCE, the Minoans were inarguably one of the most culturally advanced peoples in the world. They built huge palaces with a labyrinthine series of rooms and halls, which probably provided the basis of Greek myths about the labyrinth of the Minotaur, a half-man/half-bull monster that pursued the Athenian hero Theseus. The Minoans possessed a remarkably sophisticated drainage and sewer system and enjoyed hot and cold running water in their homes and indoor toilets. And these amenities were not restricted to their royalty but were also enjoyed by a relatively large middle class.20 As in modern Western societies, women wore clothes that accentuated their beauty instead of hiding it. Women also seemed to have shared equal status with men, and they certainly dominated the island's powerful priestly class. The surviving mural paintings of the Minoans are beautiful, too, and are quite unlike the stiff and usually menacing religious and political art seen in the Mesopotamian and Egyptian civilizations. In these murals we see charming scenes of everyday life. It appears that their artists loved creating beauty for beauty's sake. It is not unrealistic to assume that the Minoans would have become the dominant Western culture had they not been subjected to one of the most colossal volcanic eruptions to occur in the history of the human race.
Around 1640 BCE, a major outpost of the Minoan civilization, the island of Santorini (called Thera by the Greeks), was annihilated when its volcano exploded in a super eruption, ejecting an estimated 603 cubic km (ca. 143 cubic miles) of rock and ash into the atmosphere, six times more than that ejected by the 1883 Krakatoa eruption.21 Santorini was instantly transformed from a large island to a few small ones. No living thing within sight of the island could have survived. The blast generated a massive tsunami perhaps a hundred or more feet high, far larger than the one produced by the 2004 Indonesian or 2011 Japanese earthquake.22 Since Crete forms the major part of the southern flank of islands that surround the gulf in which Santorini lies, the Minoan ports bore a large brunt of the tsunami and were obliterated. Most people who did not escape to high ground were likely drowned or crushed to death by the debris of smashed ships, docks, and warehouses. Although the surviving Minoans were able to rebuild their culture, their population had been severely reduced and materially weakened. Obviously, their military strength was also greatly diminished. Not long afterward, Greeks from the north began settling on the island, whether by force or peacefully, we do not know. The Minoan culture gradually disappeared, and only the names of a few of their gods and settlements survived into Greco-Roman times. Their language, preserved on a few inscriptions called “Linear A” by archaeologists, remains undeciphered.23
However, although the extinction of the Minoan civilization undeniably altered the course of history, it does not relate to our main inquiry here. What does concern us is the fact that the Minoans created a reasonably strong concrete. The volcano that wiped out this civilization had already erupted several times in the past, long before modern humans lived on Crete, and each eruption blanketed the islands of the eastern Mediterranean with a thick layer of pumice and ash. This volcanic “earth,” rich in aluminosilicates, would later become known as “pozzolanic soil,” a name derived from the town of Pozzuoli, Italy, where nearby Mount Vesuvius had been periodically depositing volcanic pumice for thousands of years (its most famous eruption wiped out the Roman towns of Pompeii and Herculaneum in 79 CE). Engineers now refer to such ingredients in concrete and mortars as “pozzolans” or “pozzolanas.” Fly ash (ash from coal-fired power plants) and most kilned clays are also rich in aluminosilicates and are also classified as pozzolanas. High aluminosilicate volcanic powder does not need to be baked first, for Nature has already kilned it, and so it can be used straight from the ground. When pozzolans are mixed with lime, a remarkable transformation occurs when water is added: the two active ingredients combine to create a far harder and more durable material. This material is not only highly impervious to water and weathering but can actually set underwater, unlike strictly lime-based mortars or concretes for which exposure to air is necessary for the setting process. For this reason, concretes and mortars with these properties are called “hydraulic,” and the pozzolanic portion is referred to as the “hydraulic element” or “hydraulic ingredient.” Pozzolana is what separates Roman, natural, and modern concretes from the lime concrete used for thousands of years since the Neolithic period.
That the Minoan concrete was not as hard as later concretes is due to the fact that their building craftsmen were still experimenting with the material, sometimes choosing clay instead of sand as the mixing medium. No doubt they liked the more plastic qualities of clay, a malleability made more convenient by its slower setting period. The Minoans used their various concretes for floors, for foundations, and as a water-resistant mortar. They also laid some of their terra-cotta drainage and sewer pipes in this concrete,24 perhaps to prevent their breakage during earth movements (Crete is regularly subjected to strong earthquakes). Sadly, just as the Minoans' use of concrete began to expand in the seventeenth century BCE, their empire suffered the shock of the Santorini eruption.
Sometime around 700 BCE, a large, rectangular stone cistern was constructed on the island of Rhodes in the city of Kamiros (Kameiros in Greek). Kamiros was the principal city of Rhodes at this time, and was famed for being the birthplace of Peisander, a poet whose epic Heracleia, about the labors of Hercules, was ranked just behind the works of Homer and Hesiod by the ancient Greeks. The cistern held 605,600 L (ca. 160,000 gallons) of water, enough to support four hundred families. What makes this cistern unique is that the bonding agent was a hydraulic mortar utilizing lime, pozzolanic earth, and sand. It is the earliest known true hydraulic mortar, essentially pre-Roman Roman concrete without the heavy aggregate. It is not known whether or not the local masons understood the unique properties of this mixture, but its hydraulic nature was certainly ideal for a cistern. Down through the centuries, brickmasons and stonemasons have been known to be notoriously reticent about disclosing their mortar formulas.25 This secrecy about their tradecraft, related in numerous stories, has endured up to the present. If the masons in ancient Kamiros truly understood that they had something special, it's likely they kept it to themselves, for we do not see this kind of mortar used in any of the pre-Roman sites in the Greek world. It seems to have disappeared after the cistern was constructed. Kamiros was twice destroyed by earthquakes before the Common Era and was eventually abandoned. Perhaps the last stonemason or two who were privy to the formula were killed when the earth shook and their shops collapsed on top of them. We will never know. What we do know is that a similar product was discovered centuries later on the Italian peninsula, near the Bay of Naples. The ancient Romans were the first people to recognize the full potential of this novel material. And they used it to create some of the most spectacular and enduring edifices in the world.