Old New-Gate Prison and Copper Mine is one of the oldest prisons in the United States, and it's located in East Granby, Connecticut.

The site was exclusively a copper mine originally, but it was abandoned because it was never very profitable.

After the site was abandoned as a copper mine, it became a prison from 1773 to 1827.

During the American Revolution, loyalists were imprisoned at the site.

The site was eventually abandoned by 1827, and the prisoners were moved to Wethersfield State Prison

Curator and Site Administrator Morgan Bengel says visitors who come to Old New-Gate Prison and Copper Mine can self-guide and explore the prison yard.

Bengel says people can explore the copper mine on a guided tour. The copper mine was all hand-done with rudimentary blasting materials, hand-chiseled.

The site is still very dark, and very wet.

Bengel says visitors can experience the same conditions that prisoners would have over 200 years ago.

There's also a solitary confinement, which often is flooded, and that would’ve been used as punishment to separate the one man from the rest of the group.

Fragments of green copper veins are strewn throughout the ground's tunnels.

The tunnels were built as they were following the copper vein.

The men who were incarcerated lived and slept in the mine -and they would have come above ground to work in workshops - making nails or shoes or anything that could have been sold for profit.

Old New-Gate Prison and Copper Mine officially opens for the season today.