In northeastern Poland, the ruins of a massive granary overlook the Narew River.

A floundering Polish shipyard was once the soul of the Solidarity movement that capsized communism.

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

An abandoned Jewish sanatorium is tucked within the woods of Poland.

What was once an underground Nazi city is now Europe's largest bat reserve.

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

A mysterious structure left behind on the Polish mountainside, sometimes called "Hitler's Stonehenge".

Inside this Krakow church, an explosion of psychedelic color.

This centuries-old wooden wonder was built in less than a year and is one of Europe's largest timber-framed churches.

At first glance, this area seems like just another city park, but the lush landscape hides a dark past.

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

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

Museum dedicated to "the man who moved the Earth."

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

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

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

This man-made mound monument was built out of soil from all across the Polish empire.

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

Warsaw's fantastically preserved gasworks...almost.

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.

The site of the first battle of World War II.