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

In the midst of a living monument to Soviet social engineering, Polish Catholics built this church by hand.

A national collection of Communist-era musical posters.

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

Naturally formed rock city in Poland.

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

Order “Proletariat’s Cutlet” at this communist-themed restaurant allegedly once visited by Lenin.

This sprawling concrete suburb of Kraków was designed by the Soviet Union as the model proletarian city.

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

The world’s narrowest house makes for an awkward, four-foot-wide living space.

The unsettling remnants of a torn down movie set lies nearby the ruined location of the actual Płaszów Labor Camp.

Warsaw's fantastically preserved gasworks...almost.

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

After the famous composer died in Paris, his sister snuck his heart out of the country to honor his wish that it be buried in their native country.

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.

The site of the first battle of World War II.

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

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

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.

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

An underground city of salt.

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