This open-air museum was originally a World War II testing ground for German missiles and rockets.

This mysterious and once-grand memorial still embodies a remarkable architectural vision.

The hollow trunk of this 650-year-old tree was used as a hideout by two Jewish brothers during World War II.

This antique thermometer honors the creator of the first universal temperature scale.

These rare statues are one of the few remaining material witnesses to Old Prussian culture.

One of the largest amphitheaters in Europe is a former Nazi gathering place that still stands today.

A memorial to the beloved brown bear that served in the Polish army during World War II.

A mysterious emblem tucked in an small alleyway is actually the coat of arms of a heroic medieval family.

A floundering Polish shipyard was once the soul of the Solidarity movement that capsized communism.

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

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

Boats must transform into railroad cars to navigate this Polish canal.

This centuries-old wooden wonder was built in less than a year and is one of Europe's largest timber-framed churches.

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

This hidden collection of everyday objects illustrates life within communist Poland.

Poland's oldest salt mine has nearly everything one needs to live underground forever.

Deep in a Polish forest, this collection of Iron Age megaliths still holds onto many of its ancient secrets.

A striking public sculpture representing the period of martial law in Communist Poland.

A haunting deserted hotel is a favorite with artists and photographers.

A statue honors the children who fought Nazis in Poland.

A menacing statue of this mythical creature can be seen at the legendary site of the monster's lair.

The silly symbol for an underground protest group is now scattered around the city.

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

These massive moving sand dunes have swallowed an entire village and are still on the run.