Reflecting the azure color of Lake Carrera, South America's second-largest freshwater lake, the Marble Cathedral is considered to be the world's most beautiful cave network. The result of glacier movements millions of years ago, the cave is now a popular destination for photographers, who come in droves to capture this magnificent place. Getting here, however, takes some serious devotion. After arriving in Santiago, Chile, fly an additional 800 miles to the small city of Coyhaique, and then hop in a Jeep to traverse 200 miles of dirt roads. Don't worry — it's worth it.