Some of the Earth's most incredible features lie beneath its surface. Caves often hold fascinating secrets, from the world's largest underwater cave, which is full of human remains, to the Cave of the ...

Add Yahoo as a preferred source to see more of our stories on Google. The interior of the Cave of Crystals in Mexico with a person for scale. The Cave of Crystals is an underground cavern filled with ...

These huge gypsum crystals in Mexico's Naica caves, some up to 12m long, have been growing for tens of thousands of years -- but scientists have only now discovered what's inside them. "We've ...

The Cave of Crystals is an underground cavern filled with tree-size gypsum crystals, including some of the largest natural crystals ever found. The cave is located around 980 feet (300 meters) deep ...