This easily overlooked memorial immortalizes the scars from the 1956 Hungarian Revolution.

In the summer, the area around this sculpture transforms into a vibrant concert venue.

This 13th century Gothic brick castle is the largest in the world by surface area.

At first glance, this area seems like just another city park, but the lush landscape hides a dark past.

Museum dedicated to "the man who moved the Earth."

A tribute to the Polish insurgents who fought in the failed attempt to end their city's Nazi occupation.

St. Mary's features one of the most spectacularly decorated cathedral interiors in all of Europe.

This Nazi ruin was the site where Hitler was almost blown up by a suitcase bomb.

The former Nazi concentration camp stands as a museum to remember this dark chapter in European history.

An underground city of salt.

The celebrated eyesore created by starry-eyed sweethearts.

A popular shrine where the Blessed Virgin allegedly appeared in 1830, displaying a holy armchair and two incorruptible remains of Lady Saints.

Twelve grave-faced marble angels guard the emperor's tomb at Les Invalides.

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

19th century pendulum and a clock restored by a rogue group of guerilla artists.

A floating cat sanctuary on an Amsterdam canal.

A 90-foot-tall psychedelic "tree" on the side of the highway has baffled passersby for decades.

The fifth-longest natural arch in the world, and the longest outside China.

Giant, natural amphitheaters made of delicate geological formations called "hoodoos."

This rugged area of red rocks and arches is often considered one of the most beautiful places on Earth.

The only standing town in the United States that early Chinese Americans built for themselves.

Art Deco stylings conceal the true nature of this bridge.

Pillars made of 700 pieces of luggage climb to the ceiling of Sacramento Airport's baggage claim.

This 19th century hydroelectric powerhouse was the first of its kind.