An electrical pylon under whose legs a normal gauge train can run.

No need to strap in for a "ride" on this walkable roller coaster.

The first recognized Neanderthal remains were found in this now-lost cave in 1856.

Reminders of the Battle of Berlin still scar the railway.

The walls of Germany's Parliament still show the scars of the Red Army takeover in World War II.

Residents of Berlin take their coffee and cake in one of the city’s most restful spaces: a cemetery.

You've probably seen these distinctive orange-tiled columns on the big screen.

The site of the famous Nazi book burning campaign of 1933 remembers its "Night of Shame".

Where once there was a train station bathroom, there is now this German burger joint.

Gardens representing parts of Asia, Europe, and the Mid East are tucked away among the Soviet-style buildings in East Berlin.

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

This beloved marketplace mascot poops money and grants good luck.

An "inside out" building in the historical center of Paris, featuring Europe’s largest modern art museum.

A favorite Paris bar for U.S. expats, including Gershwin, Hemingway, and James Bond.

A haunting collection of the vanished and disappearing natural world.

This charming cobbled backstreet is the most Instagramable street in Paris, much to the residents' annoyance.

Notorious artist squat renovated into legal studios.

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

An early 20th-century sanatorium, long abandoned and now being reclaimed by nature.

Despite its grandiose name, this enigmatic first-century void under the town is no cave, and it's possibly not a palace either.

Spanish architects used seized Muslim gravestones to rebuild parts of the fortress.

Spanning the El Chorro gorge, this pathway used to be one of the most dangerous crossings in the world.

The hidden ruins of an old hydroelectric plant reclaimed by nature.

One of the most spectacular bridges in Spain spans a narrow chasm that divides the city of Ronda.