Old New-Gate Prison and Copper Mine
East Granby, Connecticut
This unique attraction hybrid opened as America's first copper mine in 1705, then was turned into Connecticut's first prison. At first, convicts were simply locked in the mine, 80 feet below the surface. Later, above-ground workhouses and an enclosing 12-foot-high stone wall were added, and the complex -- notoriously inhumane -- housed over 100 inmates (including women) until it closed in 1827. It sat abandoned until the 1870s, when candlelit tours of the mine began. By the early 20th century the prison's ruins had become a historical attraction, sort of, complete with a dance hall and zoo.
The state bought it in 1968, then ran out of money in 2009. The prison was abandoned again until it was reopened to the public in 2018.
A walk through the mine is still part of the tour, although those inclined toward claustrophobia may want to stay on the surface.