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

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

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

The Polish capital has had a deep connection to its guardian mermaid for almost a millennium now.

A statue honors the children who fought Nazis in Poland.

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

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

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

This Nazi ruin was the site where Hitler was almost blown up by a suitcase bomb.

A fairytale Gothic castle steeped in Nazi treasure conspiracy theories.

A program of Communist glamour in post-Stalin Poland is preserved in this colorful museum.

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

Tiny memorials honor individual victims of the Holocaust.

This water-tower-turned-high-end-apartment building was once the site of an early Nazi concentration camp.

Cold war icon and onetime "hole" in the iron curtain.

A monument to the man who almost killed Hitler.

One of downtown Berlin's last reminders of its Communist past.

Berlin's old airport.

Super-heavy Nazi architectural experiment.

On the Spree bank, discover one of the last reminders of a symbolic wall that divided, and was torn down by the people.

For the holidays, the tallest broadcasting tower in the Netherlands turns into one of the world's tallest Christmas trees.

The 20-mile causeway that separates the Netherlands from the sea.

This old KLM airplane cut into three parts was transformed into an eclectic airport gift shop.

This hotel was once home to a steamliner company and became the final rest stop for Europeans heading to the New World.