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

This enchanting natural park is a magical example of a temperate rainforest in Europe.

Statue of a decomposing prince that once held his heart in its hand.

The tombstone of an unfortunate explorer who disappeared in the Paris Catacombs.

The largest crypt ever constructed in France was built in the 11th century on an ancient Druid sacred site.

The site of the first medieval crusade that pitted Christians against Christians.

This triumphal arch celebrating the Sun King's conquest of Lille is a masterpiece of military architecture.

Ivy-covered Medieval tunnels cut through this charming town in France's Loire Valley.

This 11th-century castle sits so low you can't see it behind the surrounding buildings.

A tiny chapel perched along a 14th-century bridge.

This medieval sanctuary's tree-framed door looks like a portal to a mythical realm.

Roman ruins, natural methane fires and a lovely beach.

This Florida sinkhole hides a rainforest-like micro-environment in its depths.

These remote Florida islands have a history of sea turtles and sunken treasures, and one of the world's largest coastal brick fortresses.

The mysterious 855-foot zigzagging stone wall has been baffling people for centuries.

This kitschy tavern is also home to rare early editions of "Treasure Island."

Georgia's first brewery is also one of its oldest surviving buildings.

Crumbling ruins mark the site of a couple's grisly murder in the woods.

Cozy basement bar sports an inventory of over 2,000 beers.

This captivating Bronze Age timber circle spent centuries concealed by the tides.

The remains of 50,000 World War I soldiers rest under a towering arch overlooking the Alpine battlefields.

A cone-shaped top and cylindrical body set this 900-year-old structure apart from other Italian bell towers.

A fantastical bed and breakfast with magically unique rooms.

This historic island prison holds one of the dungeons from the Count of Monte Cristo even though it is a work of fiction.