It took the waves more than 6,000 years to craft the distinctive swirling walls of the Marble Caves in Chilean Patagonia. For centuries, water from General Carrera Lake carved swirls on the calcium carbonate, unveiling smooth, undulating patterns of blue.

The caves, aka Cavernas de Mármol, are located in the center of General Carrera, a glacial lake that spans the Chile-Argentina border. They've been hailed as a "bucket list" destination, although getting there isn't easy.

As Travel and Leisure points out:

"Traveling to the caves is a feat. The caves are about 120 miles from the city of Balmaceda, which is a two-and-a-half-hour flight from Santiago. After driving those 120 miles, which include remote dirt roads, travelers will reach a lake, at which point a boat is then required to enter the caves."

Tours take admirers to see the caves, which lurk underneath a rather bland exterior of everyday stone. Once visitors are up close and personal, however, they're awestruck by the impressionistic tunnels. The cavern's colorful blue walls reflect the lake's waters, according to Atlas Obscura, so they change in intensity and hue, depending on the time of year and on water levels.

The Marble Caves are located in the Aysén region of Chile, which Lonely Planet named one of the top offbeat regions to visit in 2017. The editors say, "Aysén is to outdoor enthusiasts what the Sistine Chapel is to art-lovers: a masterpiece worth the journey."