This massive blockhead sculpture hides an entire library.

Notorious artist squat renovated into legal studios.

This picturesque abandoned home is rumored to be a spite house.

A silly medieval mural preserved on the side of a Viennese house.

Beautiful Austrian natural history museum with carved ceilings and row after row of ancient taxidermy.

A small museum filled with over 1,000 clocks, and one particular clock calibrated to run until the year 9999.

The crypt of the imposing Stephensdom holds royal intestines and thousands of skeletons.

Macabre museum devoted to historical Viennese murders.

The final resting place for the remains of 143 Habsburg royalty.

After a nearly successful attempt on Hitler's life, the conspirators met their fate in the courtyard of this Berlin building.

Blitzkrieg bop your way through Berlin's Ramones Museum.

A fascinating insight into daily life in the Eastern Bloc.

The oldest stone house in Paris was built by its most famous alchemist.

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

France's most famous cemetery, with some of its most curious tombs.

The exact whereabouts of this surreal cabinet of curiosities are rarely the same place twice.

This boulder with a 200-word legal dedication to God has remained hidden in the woods for over 150 years.

These wire animal sculptures commemorate the exotic inhabitants that once called the Tower of London home.

The former locus of Boston's high culture has been shuttered and buried for over 70 years.

Museum dedicated to the terror regimes of Hungary.

This Hungarian castle was built out of cardboard and wood until it proved so popular that it got upgraded to stone.

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

Stumps of an Ice Age forest, visible only at low tide.

A subterranean shelter remains intact under a busy Paris railway station.