See the sky in a new way through this art installation.

The discovery of an old wall led to the creation of this fascinating museum about the city in the Middle Ages.

Now a hotel, this former bank was the site of a robbery that spawned a psychological phenomenon.

The library's graceful rotunda is like a bibliophile's temple.

Sweden's first nuclear reactor, R1, can be visited 25 meters underground.

It houses the remains of a 17th-century version of the Titanic.

Stockholm's decidedly unique public transit system has doubled as the world's longest art gallery for decades.

This ordinary street was made infamous by a legendary visit from the devil.

An enormous playhouse designed to look like 21 stacked Lego bricks, with another 25 million colorful Legos inside.

This colorful artistic feature atop a Danish art gallery allows visitors to stroll through a rainbow.

The de facto symbol of Copenhagen is this bronze fairytale which cannot seem to keep its head for very long.

Vortex-shaped aquarium hosts Europe's largest school of piranhas and other ocean creatures.

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

An ultra-modern diversity park in Denmark has turned an entire city block electric pink.

Hidden in the courtyard of the Victoria and Albert Museum is a little-known tribute to two celebrity pooches.

The canine-themed book collection claims to be Europe's largest dog library.

A movable feast that is an East London institution.

The remains of an ancient Roman teenager are memorialized at the base of a modern London landmark.

A glorious pub known for a spiteful printing feud and its famous typeface lost—then found—at the bottom of the Thames.

Pop culture has helped to keep this iconic British building from being destroyed.

Collection dedicated to brands, packaging and advertising.

London's old-school healing garden.

A makeshift shrine to the late rock star is still kept up on the nondescript façade outside 1 Logan Place.

A historic London pub with prison cells in the cellar and a "spy room" on the second floor.