A World War II torpedo launch station abandoned off the Polish coast.

The final resting place of more than 200,000 people, this is one of the largest cemeteries in Europe.

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

A statue honors the children who fought Nazis in Poland.

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

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

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

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

A collection of old neon signs from all over Poland line a secluded courtyard.

This 700-year-old structure is one of the most unique architectural and historic monuments in Gdańsk.

The site of the first battle of World War II.

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

Beneath Kraków Old Town's main square lies a hologram-filled medieval market vampire graveyard wonderland.

An underground city of salt.

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

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

This stunning natural double arch, the largest in the Alps, went undiscovered until 2005.

These quaint French houses dangle precariously over a precipice.

Crammed inside this grounded passenger plane is a bar that was once a Communist hang out and is now a ratty relic.

Tall columns of volcanic basalt make up this improbable-seeming rock formation.

Visitors flock to the historic birthplace of radiobalneology for its therapeutic radium treatments.

A massive, abstract lookout tower providing a panoramic view of Prague.

A peculiar clock commemorates a historic victory won by ringing the noonday bell an hour early.

An ornate plague column – built to celebrate life – claimed the lives of numerous artisans during its construction.