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

France's national museum of scientific and industrial instruments.

19th century pendulum and a clock restored by a rogue group of guerilla artists.

Medieval museum built over Roman baths that features famous tapestries of a lady and a unicorn.

This iconic Parisian bookstore doubles as the "Tumbleweed Hotel" for traveling writers.

A museum on the history of Paris, including a set of Napoleon's toiletries, Proust's room, and relics of the Revolution.

Flamboyant architecture from the turn of 20th century.

3,000 market stands in five former Zeppelin hangars.

Medical museum that houses most notably the taxidermied remains of Vladimir Demikhov's famous two-headed dog experiment.

A black cat protests the City Guild in Riga's Old Town.

Macabre astrological automaton clock dating to the late 1400s.

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

A museum of alchemy and a basement laboratory all housed in an ancient building in a Gothic tower.

Danish tourist destination well known for open stalls where vendors sell marijuana on the street.

The old observatory in Copenhagen has a spiral corridor used as a racetrack.

Copenhagen's celebrated theme park and gardens.

Thousands of tourists and residents in Cologne affix "love padlocks" on the Hohenzollernbrücke Bridge to symbolize their affections.

Model Trains and Much More in Hamburg.

Böttcherstraße's bells, extolling Nordic virtues and the great conquerors of the world.

Started as a kitchen garden, now the second largest botanical garden in the world.

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

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

Super-heavy Nazi architectural experiment.

Berlin's natural history museum houses the world's largest mounted dinosaur and the late beloved polar bear Knut.