This lake-bound geographical marker sits at the point where three European countries intersect.

The stones of this Incan wall complex fit together so well you couldn't fit a piece of paper between some of them.

This stream-carved gorge has inspired poets, hidden smugglers, and trained soldiers, all without losing its beauty.

The longest and tallest aqueduct in Britain can actually be sailed across.

The oldest Roman lighthouse still in use.

Climbing Iceland's highest peak on the rim of the Oræfajökull volcano.

The most iconic structure in Scotland has been home to bishops, colonels, and Sean Connery characters.

The world's oldest map of the holy land gives us a fragmented glimpse of the layout of biblical nations.

This cramped crevasse saw the entire population of its island suffocated inside its depths.

One of the oldest and certainly best preserved Cistercian abbeys still in existence.

Unusual, mushroom-like rock formations caused by weathering and water erosion, set to disappear, according to geologists.

This series of underground chambers contains Europe's largest subterranean lake that is slowly drained each day.

Once the local rulers had gone these enchanting ruins housed common folk in an almost real life fairy tale.

Once described as the "Eagle's Nest," this ruined ancient city rests on a remote mountaintop.

The remains of this ancient fortress atop a manmade hill look as though they were built into a volcano.

This fairytale castle was built as a show of power but was nearly torn down thanks to its history of torture.

This tumultuous Icelandic lava field looks so alien European researchers want to use it as a stand-in for Mars.

The world's largest neutrino telescope searches for secrets of the universe at the South Pole.

A massive underwater sinkhole made famous by Jacques Cousteau.

On the Oregon coast there is a natural hole that seems to be draining the sea.

The villagers of the coldest inhabited place on Earth adjust to unique challenges presented by day-to-day living.

These warring psychedelic crags commemorate an unsuccessful military operation.

These jagged limestone blades cut out through the canopy of the jungles of Borneo.

Breathtakingly blue walls shimmer inside the "Glacier Behind the Town."