Tribeca’s AT&T Long Lines Building is a prime example of Brutalist architecture, with its hulking slab form and imposing concrete facade. But what really draws curious gazes is its lack of windows.

Pair this with the fact that the 550-foot telephone exchange tower was built to withstand a nuclear blast and keep 1,500 people safe from toxic radiation for two weeks, has three subterranean floors, and isn’t illuminated, and you’ve got quite the case to back up reports that the building is a secret NSA spy hub (h/t TRD). 

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