Apartment complexes built into huge repurposed natural gas tanks.

Giant WWII fortresses that fired 8,000 rounds a minute, now home to thousands of pigeons.

Baroque celebration of the end of the Great Plague of Vienna.

Eighty million natural history specimens call this gargantuan museum home.

Holy Hindu shrine in an enormous, monkey-filled limestone cavern.

A battle between nature and architecture in the Cambodian jungle.

A succession of eerily contemplative iron figures lead from a Scottish museum to the sea.

A book bound in the skin of an infamous criminal, along with countless other specimens.

There are plenty of wonderful panoramic vistas in Edinburgh, but not many are hidden smack in the middle of the Old Town.

The old tradition of drying laundry on poles in the public green is still guaranteed by Glasgow city law.

A scattered trail of street art adds a pop of color to the city's stark structures.

A statue in Budapest's Liberty Square honors the former U.S. president's efforts to end the Cold War.

A museum dedicated to a secret military hospital hidden beneath a castle in Budapest.

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

Budapest's Communist-era statues, banished to the suburbs.

Built in 1870 at the bridge that connected Buda and Pest, this spectacular incline railway was almost lost forever during World War II.

Museum dedicated to the terror regimes of Hungary.

Once the home of a hermetic monk, this cave now houses a small church.

A trail of iron footwear stands as a monument to the thousands executed along this riverbank during WWII.

The walls of Germany's Parliament still show the scars of the Red Army takeover in World War II.

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

Thousands of coffin-like pillars make up this controversial Holocaust memorial.

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

At just six feet two inches deep, it is said by Guiness and Ripley to be the world’s narrowest freestanding office building.