An underground city of salt.

A 20th-century picture show in 3-D.

This Communist-era residential block is one of the longest residential building in Europe.

Memorial to the lost dead of Gdansk, whose resting places were destroyed during World War II.

This fairytale inspired, warped building houses restaurants, shops, and a radio station.

A restaurant and observation deck built in a unique broadcasting antenna.

Metro station with a claim to rock n' roll fame.

Berlin's old airport.

Bohemian paradise covered in majestic forests.

Naturally formed rock city in Poland.

The walls and ceiling of this Polish church are decorated with thousands of skulls, with another 21,000 skeletons just below.

Relive a Polish uprising via an enormous, century-old cyclorama.

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