Stockholm's narrowest alley is barely over two feet wide.

A plaque marks the house in Stockholm where the French philosopher René Descartes lived up until his death.

A wooden street sign is the last remnant of this 400-year-old alleyway.

This small museum nestled inside a souvenir shop is dedicated to Sweden's most well-known toy.

This pair of unsuspecting buildings are in fact the very first modern skyscrapers in Europe.

This statue and park honor the Swedish chemist Jacob Berzelius, one of the founders of modern chemistry.

When this 18th-century observatory's meridian was moved, it set Sweden's time back by 0.04 seconds.

An illuminated manuscript comprising the life's work of a lone monk, inexplicably decorated with a portrait of Satan himself.

There are hidden patterns on the subway seats of some Stockholm metro cars.

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

A golden plaque marks the site of the mysterious unsolved assassination of the former Swedish prime minister.

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

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

A collection of noses tucked inside an art museum reveals how times have changed.

Bored potato-guarding Nazis etched their thoughts onto a brick storage building in Copenhagen's Meatpacking District.

The final resting place of the author who gave us the Little Mermaid, the Ugly Duckling, and many more beloved fairy tales.

An old Danish political institution where members of government can grab a drink off the record.

This bridge's unique architecture honors nautical heritage and encourages self-awareness.

The world's first combination ski slope and power plant.

The art museum is decorated with creatively remodeled pre-Nazi swastikas.

Copenhagen's celebrated theme park and gardens.

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

This contemplative sculpture made out of old machine parts is meant to be the first in a series of sculptures around the world.

Beneath Denmark's Højbro bridge, a bronze merman and his seven sons forever mourn for the mother and wife who left them for land.