Dug as a secret royal escape route, the tunnel became a wartime bomb shelter and dumping ground for vintage cars.

Over 50 exquisite hand-painted Renaissance maps decorate a Medici storage room.

Go inside to really appreciate this 500-year-old technological masterpiece.

This long, dark tunnel is open to hikers, but those without lights are known to get confused even on the straight path.

Twin Peaks' real life Double R Diner has been restored to its damn fine television look.

The "Seinfeld" diner.

One of the most enjoyable bits of history at Coney Island and “the most romantic ride in the world.”

You may get stranded and everyone's peeing in the water, but at least there's cocktails!

A focal point of the Cuban government, this city square features one of the most iconic images in the country.

Hundreds of lucky felines haunt the ruins where Caesar was murdered.

The world's only museum devoted to the wonders of fluorescence.

Notorious artist squat renovated into legal studios.

The vast, legendary catacombs hold secrets much stranger than stacked bones.

Vibrant street art created with mixed media.

This massive fiberglass Gulliver turns every visitor into a Lilliputian.

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

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.

A Neolithic burial tomb connected with a colorful array of legends.

One of the few remaining casualties of the London Blitz, this destroyed church has become an enchanting public garden.

The gorgeous library at Trinity College is home to remarkable treasures of Irish identity.

This neon blue river gets its color from a unique mix of bacteria and volcano minerals.

Underwater art project will double as a massive artificial coral reef to help regenerate the damaged ecosystem.

Clap your hands at the base of the pyramid, and the song of a sacred Mayan bird will echo through the air.