For tens of thousands of years, caves have captured and fostered the human imagination. They're the closest thing to an alien world most of us will ever experience, and much like the bottom of the ocean, they continue to demonstrate how little we know about our own planet. Here's a look at some of the world's most stunning, inspiring, and spectacular caves.
Marble Caves (Chile)
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.
Credit: Linde Waidehofer / Barcroft Media / Getty Image