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

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.

A king's bloodstained shirt is among the gruesome collection of artifacts displayed below Stockholm's Royal Palace.

A concrete mushroom that divided Stockholm residents for nearly a century.

The only retired U.S. nuclear missile silo that is open to the public.

A research lab and hands-on museum where visitors can experiment with retro technology.

This tea house was a hand-built gift from Boulder's sister city in Tajikstan.