NSA uses towering, windowless skyscrapers, and fortress-like concrete structures that were built to withstand earthquakes and even nuclear attacks. Thousands of people pass by the buildings each day and rarely give them a second glance because their function is not publicly known. They are an integral part of one of the world’s largest telecommunications networks – and they are also linked to a controversial National Security Agency surveillance program. Atlanta, Chicago, Dallas, Los Angeles, New York City, San Francisco, Seattle, and Washington, D.C. In each of these cities, The Intercept has identified an AT&T facility containing networking equipment that transports...