An expansive complex of subterranean tunnels is all that remains of one of Europe's most formidable medieval fortresses.

This tri-part waterfall is a little bit of fairytale beauty in the heart of Luxembourg's Little Switzerland.

A whimsical bridge uses saxophones to pay tribute to two great men and the European Union.

Tintin's creator is celebrated in an immersive museum that's an astounding work of modern art.

A bridge that has seen many reiterations over its lifetime.

Old ships and machinery fill a historic harbor in the city that's home to Europe's largest port.

A dramatic art installation features a BMW flying out of a building in Rotterdam.

It appears as if a man is standing behind this giant airport clock, painting the hands in real time.

These slanted cubic abodes are a creative if odd solution to a zoning pickle.

Invisible bridge parts the waters, invoking biblical images and preserving the ominous feel of an ancient moat.

Birthplace of the "Cat in the Cradle" and a cluster of iconic, original windmills that let the Dutch tame the seas.

If a glacial river suddenly diving into a sheer chasm via a dramatic, multi-stage waterfall isn't peak Iceland, it's certainly close.

This valley of hot springs and boiling mud pots is home to the record-holding "Geysir," which originated the English word.

This eye-popping Icelandic crater lake is surrounded by red volcanic rock.

One of the tallest buildings in Iceland, and perhaps, the most visually impressive.

Medicinal spa created with the discharge from a geothermal energy plant.

These unusual rooms on wheels are holdovers from the 1960s.

This towering church is home to a world-famous organ and a treasure trove of medieval art.

A derelict bit of infrastructure from the canal that once ran through D.C. is landlocked in the heart of the city.

The innocent intentions of this monument are somewhat lost in the sculpture's muscled imagery.

Washington's iconic carousel has a nice piece of Civil Rights history.

A museum cafe showcases Native American dishes and indigenous ingredients from across the Western Hemisphere.

Sit where JFK proposed to Jackie or where Nixon dined on meatloaf at this storied pub.

This lighthouse was witness to the end of WWII hostilities and now collects creepy cairns.