One of the largest amphitheaters in Europe is a former Nazi gathering place that still stands today.

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

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

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

This imposing 20th-century castle was abandoned before it was ever completed.

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

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

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

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

A tribute to the Polish insurgents who fought in the failed attempt to end their city's Nazi occupation.

St. Mary's features one of the most spectacularly decorated cathedral interiors in all of Europe.

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

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

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.

A hidden art gallery in an abandoned Warsaw fort.

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

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 site of the first battle of World War II.

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

The oldest arboretum on the Dalmatian coast doubles as the gardens of Kings Landing in "Game of Thrones."

Croatia's towering concrete blossom grows from the site of a World War II concentration camp.

This huge metal monument is slowly being stripped to its concrete skeleton.