{Cueva de los Cristales in Naica, Mexico}

Remember Superman’s fortress of solitude? This is pretty much the real-life version. The Crystal Cave is 1000 feet below the earth in the Mexican state of Chihuahua and was discovered during a mining operation. The crystals, which are made of selenite, are massive – up to 4 meters in diameter and 50 feet long (check out the video to see geologists walking across them) and no one really knows how they grew so big. Unfortunately, you can’t visit the cave, but it wouldn’t be very comfortable anyway – temperatures in the Naica mine reach a blistering 112 Fahrenheit which is further aggravated by the 90+ per cent humidity. Not to mention if you slip, you might get impaled. Ah, well. This is what armchair traveling was made for.