What follows is Frieden's account of his experience. FLORENCE, Colorado (CNN) -- Visiting Supermax, the "Alcatraz of the Rockies," reveals nothing so much as an astonishing and eerie quiet.

This photo taken on February 13, 2019 shows a view of the United States Penitentiary Administrative Maximum Facility, also known as the ADX or "Supermax," in Florence, Colorado. This photo taken ...