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

This ruined folly was originally built to honor a failed American state that would have become "Westsylvania."

This one has sailed five times as far as Sir Francis Drake's famous ship.

This landmark church concealed a crypt packed with bones that was discovered thanks to the London Blitz.

The watery grave of Captain Bligh's famous ship.

The fully functional, submerged Vanuatu Post Office is definitely one of a kind.

Underwater volcanic eruption forms new island off the coast of Tonga.

The world is full of swimming holes, but few compare to Samoa’s idyllic To Sua ocean trench.

A desert island with both a buried treasure and a famous castaway.

The largest stone moai on Rapa Nui.

Named for the DeFoe novel inspired by a stranded sailor, this island is known for its rare plants and extreme beauty.

At the point of oceanic inaccessibility, you can't get farther from dry land without leaving the planet.

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

It might not be as impossible to reach as its name would imply, but just about.