France: Grottes de Lacave
Situated a dozen kilometer from Rocamadour, the spectacular Lacave Caves aka Grottes de Lacave are some of the most beautiful caverns in the Dordogbe Valle, which is actually full of caves and sinkholes. Lacave is a system of 12 caverns, all wet and still growing, interconnected by narrow passageways and staircases and tunnels. The caves are quite deep inside the mountain, without any natural entrances, so you need to take kilometer long underground train ride to get in. Spectacular stalactites and stalagmites, columns, underground pools, cave popcorn, terraces, and large showrooms are everywhere.