Jumping-off point for a climb up Mt. Everest is the most dangerous airport in the world.

Walled family complexes in Southern China.

The small cliffside monastery known as the Tiger's Nest is said to be the meditation site of an 8th-century Buddhist master.

Centuries-old bridges grown from tangled roots.

A natural arch offers panoramic views of Yangshuo's karst hills.

A total of 999 stairs lead visitors through a massive hole in a mountain known as the Gateway to Heaven.

A fifth-century temple improbably built into the side of a cliff.

Rock-cut caves and 7,000 Buddhist sculptures carved into the nearly sheer face of a sandstone mountain.

The second-deepest known cave on Earth, hidden in an extremely remote mountain region.

Sacred Buddhist home of some spiritual monkeys.

A Moroccan getaway in the mountain range that plays the Himalayas' stunt double.

Submerged trees jut ghost-like out of an idyllic turquoise mountain lake.

The largest catacomb system in the world.

Keshwa chaca, among the last handwoven Incan bridges, crosses Apurimac Canyon in Peru.

Spanning the El Chorro gorge, this pathway used to be one of the most dangerous crossings in the world.

A harrowing trail up a mile-high mountain.

Fabulous formations, weird and wonderful wildlife.

A fiery crater has been burning in the Karakum Desert since 1971.

270 million year-old forest of stone.

A remarkable geological formation resembling a forest made of stone.

A chain of 16 wondrous lakes formed as a result of the gradual dissolution of soluble layers of bedrock.