A hidden art gallery in an abandoned Warsaw fort.

A peculiar family mausoleum built by a German nobleman captivated by the occult.

A huge wooden clock that is so beautiful its creator was forcibly blinded.

An abandoned Nazi explosives plant founded by the inventor of dynamite is now an underground museum.

Poland's oldest surviving university building holds a wealth of historic science instruments including some used by Copernicus.

Warsaw's fantastically preserved gasworks...almost.

The site of the first battle of World War II.

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.

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

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

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.

A whimsical bridge uses saxophones to pay tribute to two great men and the European Union.

Relics from as far back as the 16th century are on display in a city known for its playing card industry.

Potato-peeling mannequins, Inca art, and a dangling tuber mobile help trace the history of fries at this Belgian museum.

Explore 400,000 years of humans' "battle against darkness" in this offbeat but thorough lamp museum.

A visionary precursor to the Internet made of index cards.

The bronzed skull of a beheaded traitor was affixed to the city gate in the 17th century.

This whimsical statue dumps water on its head to symbolize knowledge flowing into his brain. Or maybe booze.

Only museum in the world devoted to bookbinding and book arts holds a permanent collection representing five centuries.

This impressive collection of skulls and bones was gathered by an ex-zookeeper who took advantage of a pig plague.

A Cold War command center is hidden under an idyllic countryside.