33 Thomas Street (Formerly the AT&T Long Lines Building)

Location: New York, USA
Architect: John Carl Warnecke
Completed: 1974
Status: Present
Brief Overview: 

The building is a telephone exchange built to house telephone switching equipment and has an average floor height is 5.5 m. The floors are also much stronger than usual, designed to carry 200-to-300-pound-force-per-square-foot. It is often described as one of the most secure buildings in America, and was designed to be self-sufficient with its own gas and water supplies along with generation capabilities and protection from Nuclear Fallout for up to two weeks.

33 Thomas is likely a location of a mass surveillance hub operated by the National Security Agency