Ancient paintings known as the "Sistine Chapel of Cave Art."

Hitler's bleak vision of relaxation still stands as a mostly abandoned 10,000-room resort complex.

Abandoned railway line circling the city of Paris.

A tour of underground Berlin takes you through WWII air raid shelters and tunnels used to smuggle people out of East Germany.

The sound of swaying stalks in this stunning grove has been named a governmentally recognized sound.

Three bridges and one giant canyon make up this fantastic Spanish settlement.

This abandoned, turn-of-the-century astronomy hub is now the subject of more photographs than it ever took.

This 1,300 year old monastery built atop a single rock was once only accessible depending on the whims of the tide.

Do these monsters look familiar? The gargoyles on this church are all from pop culture.

A cathedral resurrected from the ashes of one of Europe's greatest urban fires.

This endearingly discomfited urinating statue commemorates the sneaky pees had by us all.

The ruins of an Estonian prison are drowning in the quarry lake where the convicts were once forced to work.

Mysterious craters may have been home to an ancient cult.

The gutted remains of this Estonian mansion are a monument to a tragic love.

Legend has it that not even Stalin could pull down the 2015 European Tree of the Year.

This abandoned fighter jet launch center is now a haunting street racing course.

This private skyway is filled with art and was expanded explicitly so that Hitler could appreciate a river.

The world's most active stratovolcano is almost always erupting.

This entire town moved to a safe location after it was devastated by an earthquake, but the remains of the original town are still around.

Thousands of well-dressed mummies below a monastery.

"Stairs of the Turks", a chalky white cliff eroded conveniently into stairs, allowing for easy pillaging.

Gorgeous views of Italian mountains and valleys form the backdrop of this unique open-air theater.

Abandoned blockhouses from Nazi Germany's Atlantic Wall erode into the sea on a French beach.

This tiny river island switches sovereignty every six months as part of a rare, centuries-old agreement.