Grand Central Terminal, Main Concourse

The Main Concourse is the city's great indoor public square: a 1913 Beaux-Arts hall nearly a city block long under a vaulted ceiling painted as a turquoise zodiac, its 2,500 gold-leafed stars laid out — famously — backwards, as if seen from outside the heavens. The four-faced opal clock atop the information booth is the most used meeting point in New York, and the ramps, staircases, and catwalk windows were engineered to move a small city of commuters without a single door in the main flow.

It nearly didn't survive. The wrecking-ball fate of Penn Station made Grand Central the landmark movement's defining fight, carried to the Supreme Court in 1978 with Jacqueline Kennedy Onassis among its defenders. Stand on the west staircase about an hour after opening, when the sun drops through the east windows in visible shafts, and the whole argument makes itself.