This fountain is dedicated to the workers who perished constructing the Fréjus Rail Tunnel.

The history and future of cannabis.

Countless grotesque faces stare out from this eerie Prague art wall.

One of São Paulo's tight urban intersections has become a haven for graffiti artists ever since a single Batman started the trend.

Baroque celebration of the end of the Great Plague of Vienna.

Go inside to really appreciate this 500-year-old technological masterpiece.

The ruins of the largest gladiatorial school in Rome are largely hidden under modern streets.

A master of trompe-l'oeil creates a stunning, tourist-fooling dome out of a flat ceiling.

You can spot this teeny tiny stained-glass window from the Bonifacius bridge.

The site of a concentration camp where inmates were made to take part in one of the largest counterfeiting operations in history is now hauntingly empty.

A haunting contrast of trains that both saved and took the lives of Jewish children in Nazi Germany.

An imperial church bombed to ruins during WWII now stands as a jagged memorial.

A memorial in the Tiergarten is a reminder of the suffering inflicted on homosexuals by the Nazi regime.

Cold war icon and onetime "hole" in the iron curtain.

A restaurant and observation deck built in a unique broadcasting antenna.

On the Spree bank, discover one of the last reminders of a symbolic wall that divided, and was torn down by the people.

A wunderkammer of mysterious objects and stories.

Thousands of coffin-like pillars make up this controversial Holocaust memorial.

An architectural oddity hides in plain sight on this iconic London bridge.

Once designed as the entrance to Buckingham Palace, this structure was later relocated and stands as a victory arch.

What looks like a normal building is really a hollow facade hiding a subway vent.

The celebrated eyesore created by starry-eyed sweethearts.

The oldest continuously operating mint in the world that has been making coins since the 9th-century.

The approximate spot where the last Grand Master of the Knights Templar was put to death.