Patagonia is one of those places in the world that's marked by its dramatic landscapes. This South American region, shared by Argentina and Chile, has soaring mountains, sprawling ice fields, towering glaciers and land forever altered by volcanic activity. With such rich, natural beauty to explore it might be hard to pick what to put at the top of your sightseeing list, but you won’t want to miss one of the most alien and beautiful sights in Chilean Patagonia: the Marble Caves.

The striated marble walls and ceiling give these caves their name and famous appearance. It’s easy to picture the formation as some sort of stronghold for freshwater mermaids, but don’t let your imagination run away with you. The Marble Caves are a natural —albeit fantastical— geological formation.

This cave system, located in the center of General Carrera Lake, was formed around 6,000 years ago by the relentless action of the lake’s waves. At a distance, you see a seemingly solid marble monolith rising from the middle of the lake, but as you draw closer, you'll notice the marble formation is riddled with a series of tortuous tunnels and caverns. They're carvings slower and more natural, but no less beautiful than the work that created Michelangelo’s David.

If you want to see the interior of the Marble Caves, you’ll have to make the journey by boat. Once you enter the watery caverns, you’ll be struck by the otherworldly collection of blues and greys surrounding you. The lake is glacier-fed, and it is the profusion of glacial silt in the water that plays a major role in the vibrant blue color and stunning clarity of the waters.

The sunlight that streams into the openings of the Marble Caves reflects off of the water and splashes the walls of the cave with different shades and patterns of blue. The shades you see swirling across the walls of the caverns also depends on the lake’s seasonal water levels and the amount of sunlight; shallow waters will create a lighter blue, while deeper waters will result in a darker blue. 

The Marble Cathedral and Marble Chapel are two of the largest caves you can explore in the system. Looking up at the soaring ceilings in these caves and down at the crystalline waters beneath your boat is nothing short of magical.

But getting to the Marble Caves is not the easiest undertaking. Before you hop into the boat on General Carrera Lake, you’ll need to drive about 200 miles on unpaved roads from the Chilean city of Coyhaique. Trust us; you won’t regret taking the road less traveled.