In the hinterlands of Serbia's capital, a giant reflective mushroom houses an aeronautical history of the former Yugoslav republic.

Nearly 40 miles and 1,000 years of limestone mines under Denmark.

One of a series of no-purpose kinetic artworks by Swiss sculptor Jean Tinguely.

A quaint Russian village in the middle of a German metropolis.

Communism's topsy-turvy effect on Poland has been brought to life in this wacky tourist trap.

A whimsical art tower at a Bavarian brewery includes a grotto for its mythical beer-brewing dwarves.

These gutted monastery ruins still stand proudly in the middle of the Italian countryside.

The hidden "ballroom" under a mansion lake was built by a criminal who ate a cyanide pill during his trial.

The island where one woman reigned as a "queen" over 30-odd Japanese soldiers who refused to believe that WWII had ended.

This skeleton-filled altar piece served as a backdrop to one of the most iconic scenes in "The Sound of Music."

Macabre symbols of death and mummies on display set the tone of this Italian purgatory church.

An unrecognized micronation declared by Greenpeace to protect the glaciers of Chile.

An unfinished complex built for children from around the world sits abandoned on the Black Sea coastline.

A Franco-era dam flooded (almost) everyone out of this centuries-old Aragonese town.

An unusual bronze bus shelter is actually an art installation commenting on the city's history with the Nazi party.

Swarms of butterflies cannot compare to the awe inspired by the publicly-funded nakedness once displayed in this sunken garden.

A pair of connected skyscrapers form this symbolic gateway.

Hidden in a metro shop under a shopping mall, this small museum tells the story of one of the world's largest urban transit systems.