This little Greek plateau is home to thousands of rustic, white-sailed windmills.

This abandoned Greek island was the last active leper colony in Europe.

Partially collapsed lava tube and cave system complete with concert hall, underground pond, and unique albino crabs.

This beautifully verdant lagoon is tucked below a massive volcano in a crater atop a black pebble beach.

Visit a surreal landscape so otherworldly NASA actually used it to train the Apollo 17 crew.

One of Antoni Gaudí's most classic buildings is well-known for its "dragon-back" design.

Construction of Barcelona's iconic (but controversial) church is expected to be completed in 2026—a century after the death of its architect.

These paved rills bring freshwater into Altstadt and could spell wedding bells for whoever stumbles into the waters.

The fairy tale castle of the "fairy-tale king."

The last remaining relic of San Francisco's glittering 1915 Panama Pacific Exposition.

An artsy hidden staircase leads to breathtaking views of San Francisco.

Sitting in the basement of a castle, the largest wine barrel in the world is bigger than most apartments.

A famed artist's inspiring work of peace and tolerance.

This "floating railway" is one of the world's oldest monorail systems.

This futuristic German television spire is actually the world's largest digital clock.

Twisted buildings adorn the banks of the Rhine river.

Thousands of tourists and residents in Cologne affix "love padlocks" on the Hohenzollernbrücke Bridge to symbolize their affections.

Hamburg's first legal sex work is relegated to a gated street that still does not allow pedestrian women.

While you wait to cross the street at a traffic light in Mainz, you might notice that the light is staring back at you.