Still water has been used as a mirror since the earliest parts of history, as we know from the myth of Narcissus falling in love with his own reflection in a pool. To make a mirror you need a flat, extremely smooth surface, with high reflectivity. The earliest mirrors that have been found are made of obsidian, a black volcanic glass, and include examples from about 6000 BC in modern-day Turkey. Polished copper mirrors have been found from about 4000 BC in Mesopotamia and about 3000 BC in Egypt. In Central and South America, polished stone mirrors were developed before polished metal ones (stone versions have been found dating to 2000 BC). Some early Chinese mirrors from the same period were made of polished bronze and copper by the Qijia culture, who lived in the upper part of the Yellow River region.