The metal leaves on this tree are engraved with the names of Holocaust victims.

High atop the Eiffel Tower is a small apartment built exclusively to entertain the science elite and make the rest of Paris jealous.

The oldest and smallest cemetery in Paris is only open to the public twice a year.

A beautiful Victorian statue shows France's enduring love of the rhinoceros.

This emotive sculpture was originally created for the 1878 World's Fair.

This recessed garden protects thousands of mountain plants by creating its own microclimates.

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

The very center of Paris is surrounded by a bevy of strange good luck rituals.

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

A spitting ode to a German serial killer.

A stunning gilt bronze relief denounced by Hitler as "degenerate art"—even though it was dedicated to the Nazi leader.

This tiny chapel withstood a massive mudslide and flash flood.

Explore this medieval cathedral by trying to spot all the malevolent monsters hiding in its beautifully colored windows.

A triumphant marble and bronze fountain depicting a 15th-century Hungarian king and his hunting party.

One of the most photographed locations in the entire city.

This massive steel pyramid can be entered by a set of jagged steps that let visitors stand in its heart.

This painting of a beloved dog will be on display at the Scottish National Gallery at long as the museum exists.

A memorial for a racecar driver who died while trying to set a land speed record on the autobahn.

During World War II, Austria's oldest salt mine was used to store thousands of pieces of stolen artwork.

A plaque bearing the names of those who dedicated themselves to protecting Budapest's Jewish population during World War II.

This tremendous timepiece was once the largest cuckoo clock in the world.

From Austrians to Nazis to Soviets, this historic Budapest fortress has a history as complex as the city itself.

The geographical center of Budapest is marked with a 10-foot-tall stylized zero.

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