An underground city of salt.

A king's pet, a pope's gift, an artist's inspiration, and a tragic shipwreck.

This unreal Portuguese palace looks as though it's made from a pile of different castles.

This elaborately decorated, fairytale-like Romanian royal palace is one of the most striking castles in Europe.

This Slovak bridge is known both for its connection to a national uprising and its UFO-shaped eatery.

A whimsical bridge adorned with decorative dragons.

This abandoned Slovenian military barracks has become a punky-political art squat.

The "dragon babies" of southeastern Europe.

Castle and secret tunnel withstood a siege until its owner was killed by the Holy Roman Empire, while sitting on the toilet.

A miniature train-ride through Slovenia's largest cave system.

This one-time health resort was used by aristocrats around the world.

Stockholm's decidedly unique public transit system has doubled as the world's longest art gallery for decades.

It houses the remains of a 17th-century version of the Titanic.

Eight naturally mummified bodies in glass coffins are housed in an underground crypt.

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

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

Museum dedicated to the terror regimes of Hungary.

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

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

These crumbling Latvian forts make for some haunting seaside ruins.

Flamboyant architecture from the turn of 20th century.

3,000 market stands in five former Zeppelin hangars.

Museum deep in the catacombs of St. Michael the Archangel Church is explored by touch, sound, and smell.

A memorial to the murdered Jews of Kaunas.