Underneath a chalk hill in France lies what Hitler hoped would be the underground launching base for a devastating new weapon.

A centuries-old complex of hand-dug stone chambers has sheltered locals in times of trouble.

Between Neo-Pagans and Neo-Nazis, these strange rock formations have a curious cult following and a very strange history.

1898 German railroad depot museum with working engines, steam train excursions, and hands-on displays.

A sprawling Baroque park with 300-year-old hydro-pneumatic waterworks.

An underground city of ancient quarry tunnels hid thousands of Allied soldiers in WWI.

An expansive complex of subterranean tunnels is all that remains of one of Europe's most formidable medieval fortresses.

This tri-part waterfall is a little bit of fairytale beauty in the heart of Luxembourg's Little Switzerland.

This unique Renaissance castle was turned into a home for Nazi occultism.

The site where one of the most famous poems of World War I was composed is preserved to honor the legacy of the work.

Hiding the longest subterranean river known in the world.

This beautifully designed star-shaped fort was the premier defense system of the late 1500s.

Ancient man-made caves underneath small town Belgium.

Be it nature, art, or abandoned military architecture this eclectic German "museum" has you covered.

This historical Netherlands fortress still bears the marks of its single siege.

Oldest Museum of the Netherlands is a true cabinet of curiosities.

A curious collection dedicated to human and animal anatomy and pathology.