A floating cat sanctuary on an Amsterdam canal.

Sofia's legislative center is continuously reinventing itself.

The remarkably well-preserved final resting place of a powerful ancient Thracian king.

An abandoned saucer-shaped monument in the Bulgarian mountains.

The possible imprisonment of Vlad the Impaler here earned the medieval castle its nickname, "Dracula's Castle."

This elaborately decorated, fairytale-like Romanian royal palace is one of the most striking castles in Europe.

This small city where almost everyone lives in the same building can only be reached via North America's longest tunnel.

The former Nazi Germany concentration camp stands as a museum to remember this dark chapter in European history.

A grand Gothic Revival basilica with stained glass depictions of Montreal's religious history has only one soul resting in its crypt.

A surreal statue honoring Prague's favorite literary son.

A turn of the century building boasting some of the most beautiful art nouveau architecture in Prague.

Macabre astrological automaton clock dating to the late 1400s.

A church of bones, decorated with 40,000 human skeletons.

The mummified right fist of a 1,000-year-old saint-king sits inside an ornate golden reliquary.

This colorful but controversial ceiling has been likened to a 21st-century Sistine Chapel.

Home of the Large Hadron Collider and the birthplace of the World Wide Web.

An expansive complex of subterranean tunnels is all that remains of one of Europe's most formidable medieval fortresses.

Once a strategically imperative naval base, portions of this Bermuda dock complex now serve cruise ships.

The world's most remote airport.

This large round boulder is said to emit spiritual power, but it may just be magnets.

This was once the center of the Birdman cult, and is now a World Heritage Site.

The largest stone moai on Rapa Nui.

This sheep farm has been forever transformed since being built for “The Hobbit” film series.

Tubing through a cave lit with glowworms is a magical underground experience.