What an incredible, incredible sight. The dark and dingy nature of underground life conjures something in our imaginations, but the Marble Cathedral in Patagonia shimmers without such requirements. The most beautiful cave on the planet? Beauty is subjective, but it is difficult to look past the case made by the cerulean pillars and vaulted ceilings of this stunner. Found on the shore of the General Carrera Lake in Chile, the Marble Cathedral is a pilgrimage well worth making.