811 Tenth Avenue
811 Tenth Avenue (also called the AT&T Switching Center) is a  skyscraper in the Hell's Kitchen neighborhood of Manhattan in New York City. It was designed by Kahn & Jacobs and completed in 1964, occupying the full block of 10th Avenue's western side between West 53rd and 54th Streets. Windowless and designed to withstand a nuclear blast, it was built by AT&T to house telephone switching equipment. "It was the first of several windowless buildings to be constructed" by the telecommunications company in Manhattan, "and it caused considerable controversy", the New York Times wrote in 1975. After 1985, it was used by the National Security Agency to eavesdrop on U.S. citizens under its Fairview surveillance program. In 2000, AT&T upgraded the facility from a "hardened Telco data center" to an "AT&T Internet Data Center," according to an AT&T fact sheet on the facility. As of 2014, it contains four 2,000-kilowatt generators, along with three 20,000-gallon storage tanks for fuel oil, to provide power during interruptions to the grid. Notes 

AT&T buildings
Telephone exchange buildings
Telecommunications buildings in the United States
Communication towers in the United States
Hell's Kitchen, Manhattan
1964 establishments in New York City
Office buildings completed in 1964
1960s architecture in the United States
Brutalist architecture in New York City