A spectacular rainbow of stained glass makes the "Pink Mosque" one of the most beautiful in Iran.

The ruins of this gorgeous clifftop castle look like something from a fantasy novel.

This castle was established by the 4th Duke of Montrose and is connected to the Buchanan Clan.

Double spiral staircases are not unheard of, but they are very rare.

Ride a dragon train into a world of dwarves.

The most visited, and possibly most controversial, museum in Germany.

This jaw-dropping 19th-century bridge uses its reflection to form what appears to be a perfect circle.

Rippling sand dunes frozen in the Arizona rock.

An exquisite tunnel of cascading flowers.

An artsy hidden staircase leads to breathtaking views of San Francisco.

This astonishingly geometric cave has inspired everyone from Jules Verne to Pink Floyd.

This stunning concert hall has become a symbol of Iceland's national recovery.

Strange rock formations tower above the river that snakes through this enchanting Icelandic canyon.

Crossing this suspension bridge feels like walking through the sky, a fitting tribute to the head of the Apollo program.