Inside this church, a monument honors the first burial site of the famed philosopher.

An ancient tree that was once the favorite of a young Swedish royal.

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

It was meant to help transport wounded soldiers to a secret underground hospital.

A statue that stood at the center of a long copyright battle.

A collection of trees from various corners of the world call Stockholm University home.

This tree was once used to calculate the decrease of the Baltic Sea.

An ancient Viking runestone hidden in plain view in Stockholm's old town.

The 19th-century home of Count and Countess von Hallwyl is now a museum.

A concrete Picasso in the middle of a student housing complex on the outskirts of Stockholm.

Sweden's first electric elevator remains hidden within a fortress-like building.

This giant subway sculpture celebrates the fruit that inspired the theory of gravity.

It is said that each of the white stones in the red facade of this medieval house represents the head of a murdered Swedish noble.

Legend says this sacred tree was a gift from goddess Athena.

This once architecturally advanced housing complex is now a haven for squatters that still bears the scars of war.

Preserved portions of Athens's ancient defenses are on display in a subterranean parking garage.

Large collection from the 3rd millennium BCE.

Once part of an ancient international harbor, it's now an all-you-can-eat shrimp buffet for flamingos and other water birds.

The animals wander freely amid this gorgeous stretch of nature.

The ruins of a fairytale castle with a tumultuous history stand high atop the mountains.

A 1970s resort city now stands abandoned, caught in the middle of a divided island.

This no man's land slicing through the island is strewn with abandoned relics of another time.

A unique configuration of blown glass can be found inside this hotel lobby.

An imperial church bombed to ruins during WWII now stands as a jagged memorial.