This national park dedicated to the tallgrass prairie ecosystem still displays its military past.

What was once the second largest steel mill in the US is now a sprawling complex of modern ruins.

A replica viking ship from the Chicago World's Fair is still in dry dock in an Illinois park.

Fragments of architectural wonders from around the globe are embedded in the newspaper building's walls.

These abandoned grain silos and tunnels are an urban exploration dream.

What's left of the ruins of the 1893 Columbian Exhibition, or World's Fair, also known as the White City.

Chicago's largest cemetery is full of beautiful Victorian monuments and more than a few ghost stories.

An enormous park-like oasis, full of famous Chicagoans' graves.

An outdoor urban gallery of large-scale artworks by the world's most influential street artists.

A museum dedicated to the history of a terrifying secret police is now held in their former headquarters.

Started as a kitchen garden, now the second largest botanical garden in the world.

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

Museum in a swimming pool where the water still flows.

A series of abstract, silly sculptures represent the works of a great modern classical composer.

This museum in a Paris apartment gives a unique look at the iconic French singer's life.

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

The vast, legendary catacombs hold secrets much stranger than stacked bones.

The first green space constructed on an elevated viaduct.

France's most famous cemetery, with some of its most curious tombs.

A majestic lion statue guards this Parisian botanical garden, and feeds on an unsettling item.

The history of radiation is on safe display at the foot of a radiation science laboratory.

This Parisian café sticks almost exclusively to an ethos of reuse.

One of the oldest medical collections in Europe focusing on rare surgical instruments.

This French ghost town from World War II has been left as a memorial to German atrocities during World War II.