Marble Caves (Chile)
Credit: Linde Waidehofer / Barcroft Media / Getty Image

Most caves are made of limestone, a sedimentary rock that dissolves when exposed to the naturally occurring acids found in groundwater. Marble is actually made of limestone, formed by the heat and pressure of metamorphic processes that combine the stone's calcite with impurities to create the colors, swirls, and patterns visible on your kitchen counter. The Cuevas de Marmol were carved out of a marble peninsula by a Patagonian glacial lake shared by Argentina and Chile. The entrances, which are on the Chilean side, are accessible by tour boats, but kayaks are also available and allow visitors to enjoy spectacular views of the Andes from the cave mouth.