Landscape architect Joseph E. Brown described the park as a “lifted landscape” that was designed to express the idea of connection. Initially, the plan was to block foot traffic on the south side of Liberty Street, where the Vehicle Security Center entrances are located, but this was an anathema to the larger goal of restoring street circulation. “Let’s get people off that sidewalk and into the park,” Lavallee said. “We convinced the Port Authority to cantilever the roof of Liberty Park, extending it like a canopy over the sidewalk.” This allowed the garage doors to be recessed and created an upper overlook onto the memorial plaza, which sits about twenty-five feet (7.6 m) below it. Asked how contemplation of the memorial will mesh with the thunder of commercial traffic entering just below, Brown said, “People are immune to street noise in New York City,” and, as is often the case, he was right.

Memorial designers Michael Arad and Peter Walker initially dismissed the idea of the park’s overlook because they didn’t want people looking down at grieving visitors, although several million square feet of office space also have views of the plaza. Arad also felt the memorial’s solemnity would be diminished by the Vehicle Security Center’s façade, which is directly across the street. In response, the designers built a “living wall,” a 300-foot-long (91.4 m) wall of evergreen plants, including periwinkle, pachysandra, and Baltic ivy, which covers the center’s northern façade and softens the views south from the memorial. “We chuckled at first when we heard we were going to build a green wall on the north side of the building, because that’s a tough place to get plants to thrive,” Lavallee said. No matter how beautifully clad, the screening center was going to look like the massive structure it is. “Ultimately, we created a stone base on one end that effectively was the church entrance at the street level. At the other end was the landing for the bridge. Those two masonry bases were the bookends, softened in between with the green wall.”

Planters define the park’s pathways and subtly direct pedestrian traffic. They have angular, fractal shapes, a nod to the fractured aesthetic of Libeskind’s master plan and Snøhetta’s Pavilion. These jagged shapes also allow for diagonal movements through the park, making it feel less formal, especially in contrast to the memorial plaza. “We chose not to go with wiggly, dendritic shapes, but with bold shapes that rise and fall,” Brown said. “This creates a slight sense of enclosure without making people feel as though they could get lost.” To create visual variety, the planters tilt in multiple directions, angled to showcase the garden plantings as one walks in either direction. They also accommodate recycled teak benches with backs to support those with disabilities.

Visitors enter the park from all four corners via a series of staircases and ramps. The grand staircase on Greenwich Street was deliberately placed parallel to the church to direct views north to the site. Composed of stepped terraces with seating, this hospitable staircase provides a logical meeting spot and also offers a place to decompress after visiting the memorial. In the southwest corner, another series of stepped terraces creates an informal amphitheater setting. It was configured to keep people off a secure area over the Vehicle Security Center; to avoid fencing the area, the designers devised the stepped stairs, which function as a wall and frame a garden full of plantings, another deterrent to foot traffic.

To accommodate St. Nicholas, they placed it atop a stone base so that it appears to be built on a plateau, reminiscent of how churches are sited on Mediterranean hillsides. To avoid making the church feel like an obstruction that people had to walk around, they “wrapped the landscape up to it in some places,” and in others allowed pedestrians to walk along the building. Although Calatrava wanted to eliminate the park altogether so his church could sit on a flat plaza, they agreed on a curved forecourt in front of the church. Fortunately, according to Lavallee, these negotiations yielded “an open space of a scale that we didn’t have previously in the park.”

Placing, sizing, and disguising the five aboveground ventilation shafts that service the lower garage required deft planning. Typically, such shafts are a security nightmare, since people can cause air contamination by throwing things into them. Here they were located with standoff distances of ten to twenty-five feet (3 to 7.6 m) between them and the public. Since the Vehicle Security Center and its exhaust systems were designed before the park, DSP had to work around them. “We pushed and pulled the heights of these vents, twisting their shapes to allow a park to happen.… We were finally able to create standoff and security by wrapping the landscape around them in some places or by lowering the grade around them, the finished grade on the roof, to minimize their height.” The designers used strategic cladding to minimize the exhaust towers’ visual impact, covering the vent near the West Street crossing, for instance, in the same materials as the bridge so it would appear to be a part of that structure. The two vents by St. Nicholas are clad in matte glass that magnifies the greenery around it. In all cases, Lavallee said, the idea was to make the ventilation shafts “feel like architecture, intentional and not hidden with vines or other silliness.”

In many ways, the park represents in a microcosm what is best about New York City—the unexpected moments of delight that occur while walking along its teeming sidewalks. Because it is not possible, or desirable, to prescribe the actions of millions of visitors, and because so many requirements and structures had to be accommodated within a mere sixteen acres (6.5 ha), structural diplomacy was paramount. In this regard, Liberty Park represents a civilized and gracious pause in the overall scheme and is a welcome addition to lower Manhattan.