One drop of water in Mexico's giant Crystal Cave contains 200 million viruses

According to the website of National Geographic magazine, in 2000, scientists discovered a giant crystal cave 1,000 feet (about 304 meters) below the Naica Mountains in Mexico's Chihuahua Desert, which is another natural wonder. In 2008 and 2009, scientists returned to the giant Cave of Crystals in Mexico and solved many biological mysteries during the expedition, discovering an "ice palace" with four walls full of rare crystals. In the National Geographic Channel documentary "Into the Lost Crystal Caves," which premieres on October 10, viewers will once again be able to see the wonders inside the giant Crystal Caves.