adverse possession, the building's owners have closed the plaza to the public for one day every year since its completion. Within the ground-story plaza are rectangular columns clad in stainless steel, which support the second story. The columns, which extend to the underlying rock, are set behind the lot boundary to avoid interfering with the walls of the Park Avenue railroad tunnel. The column layout gives the appearance that the upper stories are floating above ground. These columns give the appearance of an architectural arcade. The second story is designed with an opening at its center, overlooking the planted garden. The third through twenty-first stories consist of a rectangular slab atop the northern portion of the site, occupying a quarter of the total lot area. The slab is only wide along Park Avenue, allowing all offices to be within of a window and thereby providing large amounts of natural light to tenants. Along 54th Street, the slab is wide. The slab's positioning, with the shorter side along Park Avenue, allowed more natural light from the north and south facades. This design also served a technical purpose, as it complied with the 1916 Zoning Resolution, intended to prevent new skyscrapers in New York City from overwhelming the streets with their sheer bulk. As a result of the slab's small size, Lever House has a floor area ratio (FAR) of 6:1, in comparison to a FAR of 12:1 at Rockefeller Center and a FAR of 25:1 at the Empire State Building. A provision under the 1916 Zoning Resolution had allowed structures to rise without setbacks above a given level if all subsequent stories covered no more than 25 percent of the land lot. This theoretically allowed the construction of slab skyscrapers of unlimited height. In practice, Lever House was the city's first high-rise building to take advantage of this provision. Previous skyscrapers developed under this zoning code had contained setbacks as they rose. If all stories had contained the same area as the land lot, Lever House would have been equivalent to an eight-story structure. While Rockefeller Center's buildings had somewhat similar slab-like designs, the vast majority of the city's previous skyscrapers had been designed to fill the maximum volume allowed under the 1916 Zoning Resolution. Facade About thirty percent of the ground story is enclosed within glass and marble walls. There are three revolving doors leading to the ground-story lobby, near