Underground lake in Ruskeala Mountain Park, Karelia, Russia

The Ruskeala Mountain Park is a spooky but beautiful reminder of the mining industry that thrived for centuries in this area of Russia near the border with Finland. Constructed on top of an abandoned marble quarry, the park opened to the public in 2005. An old quarry that's been flooded with groundwater since the end of World War II is the park's centrepiece, although some old buildings and kilns from the mines are still intact.
© Konstantin Trubavin/Offset by Shutterstock