In 1977, an eccentric book lover formed a micronation for book lovers.

A half-size replica of the World Trade Center towers above Tulsa.

The last stop in southeast Russia.

For the last century, this international border within a small town has appeared and disappeared various times.

This extremely remote border crossing was closed to prevent smuggling and looting.

The point where New South Wales meets Queensland and South Australia.

The first marker along the famous boundary.

The meeting of the northwestern corner of Delaware, the northeastern corner of Maryland, and the southern edge of Pennsylvania.

Abandoned Nazi train station turned underground astroparticle laboratory.

These ancient sunken lanes were naturally tunneled into the soft ground by countless footsteps.

This "floating island" plateau sits 7,671 feet above the forest floor.

A pyramidal marker where the borders of Venezuela, Brazil, and Guyana meet on top of Mount Roraima.

Alaska Natives have lived on this tiny isolated island in the Bering Strait for over 5,000 years.

Walk through a restaurant's refrigerator door to reach this hidden bar.

This long line of cement defensive wedges is named after the famous chocolate bar for obvious reasons.

This secret Swiss fortress is disguised as a harmless pink house, complete with fake windows.

A curious little museum dedicated to the furry feline in the cat haven that is Old Town Kotor.

A subterranean playground in an abandoned slate mine.

This tunnel entrance is built to resemble a grand castle but no one is quite sure why.

This tangled English forest looks like something right out of a fairytale.

These medieval tunnels provided water to the city above through centuries of civil war and plague.

An extraordinary collection of scientific instruments - and Einstein's chalkboard - inside the world's oldest purpose built museum building.

An Oxford museum where visitors can have tea with the Mad Hatter and climb through the wardrobe to a fantasy land.

Two nations form a rare four-sided border at the peak of a mountain, philosophical questions result.