High in the Sacramento Mountains, a facility dedicated to studying the sun.

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

The eccentric midcentury home of a suspected mafia gun-runner.

A cablecar-station-turned-revolving restaurant with 360-degree views of the Swiss skyline.

The steepest classic funicular in the world glides along a dizzying incline.

Caves famous for the dragon-slaying saint who lived there.

This Torino museum honors a soldier who kept the city safe using barrels of exploding gunpowder, losing his life in the process.

A landmark in the history of technology and computing is hidden in a tiny Baroque chapel.

When this funny little building went up in the 19th century, most people thought it would simply fall over.

This Danish castle is supposedly haunted by a woman too independent to not be a witch.

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