Warsaw's fantastically preserved gasworks...almost.

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

A hidden art gallery in an abandoned Warsaw fort.

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.

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

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

The site of the first battle of World War II.

This Polish cave has housed a dragon, a brothel, and an enduring legend.

Real bones which are said to have belonged to a Polish dragon.

An underground city of salt.

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

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