A former Latvian headquarters of the brutal KGB secret police is now open as a grim reminder of their atrocities.

3,000 market stands in five former Zeppelin hangars.

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

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

This Communist-era residential block is one of the longest residential building in Europe.

The site of the first battle of World War II.

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

This open-air museum was originally a World War II testing ground for German missiles and rockets.

This abandoned but well-preserved Prussian fortress sits abandoned in a Polish forest near the German border.

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

An underground city beneath Krakow's postwar socialist utopia.

A Soviet era flat that refused to conform to the dull gray standards.

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

While the U.S. and Soviet Union were engaged in a space race, Poland built a UFO on the ground.

The oldest wind turbine in Europe, constructed by a group of friends in 1932.

Dubbed "Wistom" by locals, this abandoned factory is an urban explorer's dream.

This biographical museum honors the groundbreaking scientist at her birthplace in Warsaw.

This extensive collection covers thousands of years of Polish military history.

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

This museum houses and extensive collection of technology contributed by the Polish people.

Warsaw's fantastically preserved gasworks...almost.

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

This lakeside bunker complex in Mamerki, Poland, housed the Supreme Military Command of Nazi Germany during World War II.

Built to transport German U-boats through the never-completed Masurian Canal, the locks near this Polish village are now home to a rope course.