Ruins of the New York State Pavilion
Queens, New York
Designed by big-deal architect Philip Johnson for the 1964-65 New York World's Fair. It's still an impressive sight even though it's closed and may eventually fall down before it's ever repaired. It's probably best known today for its pivotal role in the first Men in Black movie.
The tallest of its three towers (the highest point at the Fair) had an observation deck reached by an outdoor glass "Sky Streak" capsule elevator. The "Tent of Tomorrow," 100 feet high, shielded a $1 million floor map of New York that covered 9,000 square feet and showed the location of every Texaco gas station in the state (Texaco paid for the map). The elevator is long gone, the tent lasted until 1976, and you could still walk on the map up until around 1990, but it's all closed off now.