The vast, legendary catacombs hold secrets much stranger than stacked bones.

It's good luck to be mocked by this monkey.

Sitting in the basement of a castle, the largest wine barrel in the world is bigger than most apartments.

Noirish green neon marks the location of one of the oldest private detective agencies in France.

Metro station with a claim to rock n' roll fame.

Berlin's old airport.

On the Spree bank, discover one of the last reminders of a symbolic wall that divided, and was torn down by the people.

A tour of underground Berlin takes you through WWII air raid shelters and tunnels used to smuggle people out of East Germany.

A monument to the three wars that led to German unification towers within a Berlin traffic circle.

One of the world's heaviest musical instruments towers within a popular urban park.

Beneath the impressive baroque cathedral that rises from the center of Berlin lies the largest collection of Prussian royals in the world.

The most visited, and possibly most controversial, museum in Germany.

A narrow passage next to a cafe leads to a courtyard exploding with murals, tags, and paste-ups.

A whimsical and twisted animatronic monster tour beneath the streets of Berlin.

This baroque palace displays an impressive collection of taxidermy, art, and rare objects from the days of courtly hunting.

Fantastic views and thousands of love locks.

The celebrated eyesore created by starry-eyed sweethearts.

High atop the Eiffel Tower is a small apartment built exclusively to entertain the science elite and make the rest of Paris jealous.

A tiny chapel clings to a precipice above Germany’s gemstone capital.

The fairy tale castle of the “fairy-tale king,” this was also the inspiration for Disney’s “Sleeping Beauty.”

Ruins of a German castle on top of a towering stone pillar.

A striking 12th-century-style castle built on the edge of a cliff.

The birthplace of an eccentric alchemist and possible inspiration for the fictional reanimator of monsters.

The semi-reclaimed ruins of this canal were once part of an ambitious plan to reroute the mighty potomac.