Walking into Fingal's Cave is like walking into the heart of the Earth. Here among the towering basalt columns, the visitor stands inside a lava flow. Magma that swelled up from deep in the Earth ...

Take an otherworldly journey through Hang Son Doong, the world's largest cave located in Vietnam. The cave is more than 500 feet tall, 650 feet wide, and 29,500 feet long. Video courtesy of Ryan ...

Sistema Sac Actun, the world's largest underwater cave system, spans an impressive 215 miles. This subterranean network of tunnels and crystal-clear waterways is a geological masterpiece with ...

To stay in your cave, to be a stalactite ... mystery on the driving range and then another on the course and another inside your mind and then suddenly you stacked one good day on top of another ...

Residents take shelter in a similar cave near Hama in this photo from 2012. The civil war has been raging in Syria for almost five years. A displaced girl poses inside an underground cave in the ...

Nestled in the Staffordshire countryside, you'll find fascinating traces of Britain's last cave inhabitants and they're more comfortable than one might initially believe. On Kinver Edge ...

Discovered in 1999 inside an abandoned mine in Southern Spain, Pulpí Geode is the largest crystal 'cave' of its kind in the world. But what exactly is a geode and how do crystals form inside them?