In northern Mexico, a sealed underground chamber deep beneath the Sierra de Naica holds towering selenite formations ...

This underground cave in Iowa features rare anthodite crystals, stalactites, a cool year-round interior, and guided tours ...

More than 900 feet beneath a mountain in northern Mexico, there’s a hidden chamber that almost doesn’t look real. Massive, glass-like crystals stretch in every direction, some as long as a city bus.

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 ...