811 Tenth Avenue

811 Tenth Avenue 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 contained four 2,000-kilowatt generators, along with three 20,000-gallon storage tanks for fuel oil, to provide power during interruptions to the grid.