This "floating railway" is one of the world's oldest monorail systems.

A stairway to heaven, or to nowhere at all.

Art and a pun, all in one.

Ruins of a German Castle on top of a towering stone pillar.

Inside this Krakow church, an explosion of psychedelic color.

This picturesque castle in Poland has a rich history, including a legend that ties it to lost Incan treasures.

This 13th century Gothic brick castle is the largest in the world by surface area.

What was once an underground Nazi city is now Europe's largest bat reserve.

A 90-ton, gravity-defiant steam locomotive shoots for the skies in this bizarrely beautiful public artwork.

This imposing 20th-century castle was abandoned before it was ever completed.

Museum dedicated to "the man who moved the Earth."

The former Nazi concentration camp stands as a museum to remember this dark chapter in European history.

An underground city of salt.

Countless stories attempt to explain Poland's mysterious J-shaped trees.

Once the tallest building in Chisinau, this unique tower is a relic of Soviet architecture.

Elaborate mansions built by Roma residents in Soroca to show their success after centuries of discrimination.

This 15th-century Ottoman bridge was modified to keep up with the changing course of the river Erenik.

A UNESCO-protected spiritual seat of the Old Serbian Kingdom and Empire.

The ceiling of this cavern is dripping with multicolored marble stalactites.

Christianity and Islam have clashed, yet here a Serbian Orthodox church and a mosque stand together.

A futuristic, brutalist masterpiece that is also strangely prison-like.

A scenic UNESCO site that doubles as a habitat for various forms of wildlife.

This ominous Albanian fortress houses tanks and downed planes as a reminder of their victories over Western imperialism.

This picturesque monastery at the base of a cliff is a peaceful oasis open to all visitors.