The ruins of an ancient island city built atop a coral reef in the South Pacific are spectacular and strange enough to have inspired H.P. Lovecraft.

An ancient Thracian city where fire rituals were practiced on the largest cult altar in Southeast Europe.

A Turkish ghost town abandoned in a population exchange with Greece.

An abandoned town of skeletal wooden homes.

A fantastic castle rumored to be the birthplace of King Arthur.

Huge stone depressions which may have acted as an Incan agricultural experiment.

A once great mansion stands in stately ruin.

A sturdy relic of Britain's once crucial gunpowder industry is now a haunting Cornish ruin.

This abandoned Olympic skiing facility still bears the scars of the Siege of Sarajevo.

The ruins of this gorgeous clifftop castle look like something from a fantasy novel.

A lake at the bottom of the ocean.

A small man-controlled waterfall powers an Art Nouveau elevator and is accessed via narrow gauge, solar-powered tramway.

An explosion of natural color known as "the river that ran away from paradise."

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

Part of one of the largest flooded cavities on the planet, and littered with prehistoric animal bones.

Walk behind a 50-meter-high waterfall.

An island said to shake with the current.

Every fall this lake mysteriously drains, like a bathtub with the plug pulled out.

A sacred lake composed of over 300 separate pools of highly concentrated minerals.

Only known mainland rookery of the threatened Stellar sea lion.

This extraordinary geological oddity resembles human-made pavement.

Over 3km of caverns and caves at the Switzerland-France border contain the largest underground river in Central Europe.

Vast stretch of tide-pools with a unique Moroccan charm.

Rocky Atlantic beach home to a stunning stone arch.