The highest-security prison in the nation goes by a few different names. Officially, it’s the United States Penitentiary, Administrative Maximum Facility, part of a sprawling, four-prison complex in Florence, Colo. Colloquially, it’s the “Supermax,” or “Alcatraz of the Rockies.” But to insiders, it’s simply the ADX.

Over the past three years Arnold & Porter’s Edwin “Ed” Aro has become an insider. Aro has spent more than 160 days at the ADX since August 2011, meeting more than 150 inmates—about a third of the facility’s 450-man capacity. “[Ed's] spent more time there than anyone who does not work there or live there,” says prisoners’ rights attorney Deborah Golden.