What was once an open-pit mine, Ruggles Mine, is now a popular destination open for exploration. The pit includes tunnels and underground chambers which you can adventure through. There are some areas where you can go underwater scuba diving with the proper gear.
Ruggles Mine is an open-pit mine that was turned into a tourist attraction that is now closed and for sale. The mine is located 40 miles (64 km) northwest of Concord, New Hampshire, in the town of Grafton, a short distance from Route 4 at the village green. The spacious pit includes tunnels and underground chambers, some of which are filled with water. Visitors were allowed to keep any of the various minerals that were found on the mine floor or that could be hammered loose from the walls of the pit.Provided By: https://en.wikipedia.org/wiki/Ruggles_Mine