The 2,000-year-old Roman columns are hidden within Barcelona's Gothic Quarter.

The largest Art Nouveau complex in the world is a Barcelona hospital with a 600-year-long history.

Bask in the 19th century grandeur of an eccentric Freemason millionaire's private gardens.

This cemetery features modernist statues as strange as its name.

This semi-secret storybook hedge maze is also the oldest garden in the city.

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.

This sprawling concrete suburb of Kraków was designed by the Soviet Union as the model proletarian city.

This grubby wall is said to be one of the Earth's esoteric energy centers.

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

This Polish cave has housed a dragon, a brothel, and an enduring legend.

Real bones which are said to have belonged to a Polish dragon.

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

One of Amsterdam's narrowest houses is located right across the canal from its widest.

This city square is home to Amsterdam's oldest church and a statue honoring Dutch sex workers.

A Dutch passageway's artistic, aquatic-themed makeover pays tribute to the capital city's famed waterways.

Amsterdam's Red Light District leaves little to the imagination.

Yup, that's a 330-foot yacht passing over the highway.

This unusual elevator doesn’t stop or slow down.

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

A public urinal so pretty, it was declared a national monument.

Three connected pink triangles memorialize persecuted gays and lesbians throughout history.

Museum celebrating the ocean, with the largest wunderkammer dedicated to sea exploration.

A new sculpture calls attention to climate change in the centuries-old city it threatens.