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

The rusting hulk of a Soviet warship sits on a Polish beach.

An engineering marvel at the time of its construction, this cross-border waterway sought to connect the Black Sea to the Baltic.

A small granite monument marks where the borders of three countries meet.

The two abandoned overpasses are among the largest bridges in Poland.

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

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.

This Nazi ruin was the site where Hitler was almost blown up by a suitcase bomb.

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