The Eisriesenwelt is a natural limestone ice cave located in Austria, about 40 km south of Salzburg. It is the largest ice cave in the world, extending more than 42 km of tunnels and chambers. Only the first kilometer, the area that tourists are allowed to visit, is covered in ice. The rest of the cave is made of limestone. Entry to the caves is regulated and a 75-minute tour takes in several immense caverns containing elaborate ice formations and frozen waterfalls