The half-mile long structure is so impressive, it even shows up on satellite images.

The world of the ancient Celtic civilization explained through a bewitching 11 acre garden.

An Iron Age fort on the edge of a seaside cliff offers a glimpse into an ancient, mystical world.

An important pilgrimage site for pagans and early Christians, named for a Celtic goddess-turned-saint.

The ruins of a medieval seminary some say is the oldest university site in Scotland.

A hidden tunnel leads to an abandoned slate quarry that's now a secret swimming spot guarded by cliffs.

Accessible only at low tide, the deserted island is dotted with World War II ruins.

One of the most remote and isolated villages on the Arabian Peninsula.

This impressive system of tanks was used to store drinking water as long as 2,000 years ago.

A mad mystery man who led Canadian mounties on a 150-mile wilderness chase is still buried with his secrets intact.

The world's northernmost flowers cling tenuously to life on desolate Kaffeklubben Island.

Dead weights honor the dead of Portugal's fishing industry.

This uninhabited volcanic island is the most remote in the world.

The 20-mile causeway that separates the Netherlands from the sea.

This Shetland Islands bus shelter may be small, but it squeezes in a couch, a desk, some art, and even an old telly.

Towering basalt columns, a creation of fire and ice.

See massive fossils that are over 200 million years old in northeastern Arizona.

America's most famous museum of medical oddities is home to the remains of Albert Einstein's brain.

Fossils, railroads, and waterfalls!

Site of the first official transatlantic wireless communications.

The sign at the garden gate reads: "These Plants Can Kill."

An isolated village literally built into the crevices and rock formations of a mountain.

This fairy-tale, neo-Gothic church in the Azores is a world of magical realism.

This enormous storm barrier is one of the largest moving structures on Earth, with each arm taller than the Washington Monument.