An abandoned NSA listening post on Berlin's "Devil's Mountain."

Berlin's old airport.

Two very green residential towers cleaning the air in one of Europe's most polluted cities.

Gaudí's famously flamboyant architectural style is on full display in this sprawling park and garden.

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

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

Cozy basement bar sports an inventory of over 2,000 beers.

A 14th-century fortified keep showcases the masterpieces of an ingenious 20th-century clockmaker.

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

Rotterdammers' dirty minds gave this santa a dirty nickname and cursed it to a life of wandering.

Built by crowdsourcing, this wooden foot bridge saved a part of Rotterdam that was languishing in wait of city funding.

This 22-floor tower's Skydeck offers panoramic views of Amsterdam.

One of the Seven Wonders of the Modern World holds the world's tallest metal staircase.

An enormous, inside-out glass globe built in 1935.

An interesting decoration on this historic site, this weathervane comes with as many legends as it does questions.

A former waterfront market is now in the center of town due to some interesting Boston engineering.

Most-visited and most-photographed slot canyon in the American Southwest.

Dramatic river bend surrounds a natural red-rocked pedestal.

An homage to everyone's favorite prehistoric cartoon family.

A monument celebrating the idea of reaching inaccessible places.

The former home of the Nobel Prize-winning American writer is now home to dozens of six-toed cats.

An abandoned water sports stadium that has become a haven for graffiti and decay.

Former villa and estate of James Deering developed to preserve native tropical forests.

Hoodoos, naturally eroded land formations, stand 20 feet tall in the Canadian badlands.