This ancient hydrological marvel is now the base of a modern outdoor cinema.

Double spiral staircases are not unheard of, but they are very rare.

This large, circular tomb is the final resting place of the first emperor of Rome.

This floating garden in the sky is straight out of a fairy tale, but the real thing is nothing short of magical.

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

The world's first floating farm is staffed by one human, three robots, and 35 cows.

The ruins of this medieval castle on a foggy hill tell the story of a once-mighty empire.

Under a glass sidewalk lie the remains of some of Manhattan's oldest buildings.

Hidden within a Netherlands crater is a stone bed that lets those who lie in it see the sky as a curved surface.

Legend has it that seven Anglo-Saxon kings were coronated on this stone, located in the appropriately-named town of Kingston.

This statue of a falling man commemorates a teenage martyr of the Hungarian Revolution.

This pair of Australian "waterfalls" appear to be falling straight across the land.

The tradition of open-air secondhand and antiquarian bookselling in Paris dates back to the Renaissance.

400-year-old garden, restored to beauty.

The gilded, masterful astronomical clock will calculate time, dates, and planetary positions for thousands of years to come.

A little-known cafe in an old copper bridge tower with 360-degree views of the harbor.

Climb to the top of its spiral spire for spectacular views of Copenhagen.

A museum filled with tiny, adorable versions of the mighty Royal Danish Navy.

Danish tourist destination well known for open stalls where vendors sell marijuana on the street.

The only surviving piece of Copenhagen's 16th-century defensive wall.

Copenhagen's celebrated theme park and gardens.

Pre-Nazi swastikas adorn the sculpted pachyderms flanking this brewhouse portal.

A 19th-century subterranean reservoir repurposed as a contemporary art cave.

The old observatory in Copenhagen has a spiral corridor used as a racetrack.