World's largest cave was only discovered in 1991, and now offers tours to the public.

An unassuming music museum recounts the rags to riches story of a dramatic Portuguese genre.

In the Monastery of São Vicente resides a gallery devoted to a breathtaking collection of seashells.

Singapore's landscaping project is home to 18 incredible Supertrees.

Beneath the impressive baroque cathedral that rises from the center of Berlin lies the largest collection of Prussian royals in the world.

A surreal museum of extraordinary industrial objects.

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

This 600-year-old home seems to defy physics.

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

A brush maker used his factory to protect blind Jews from the Gestapo.

These brass bunnies honor the rabbits that dominated the no-man's-land around the Berlin Wall.

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

This mesmerizing and surreal landscape features intricate patterns of white and red sandstone.

One of the most easily accessible examples of the rare 1960s UFO houses.

Walk inside a half mile long crevice right outside the town of Garmisch Partenkirchen.

A stairway to heaven, or to nowhere at all.

Shimmering sea-colored mosaics and Jesus statues cover this opulent building.

An elevator into the Baltic Sea.

The skeletal frame of a decommissioned gas-pumping station offers breathtaking views of greater Berlin.

This 8th-century Bavarian monastery is home to an exquisite Baroque-era library.

Twisted trees shaped by coastal winds make this woodland look like something from a spooky story.

This amazingly preserved Doric temple was abandoned before it was ever completed.

A madman's personal garden filled with 1,000 sculpted heads.

Gorgeous views of Italian mountains and valleys form the backdrop of this unique open-air theater.