Stuðlagil, Iceland

Prehistoric in its appearance, Iceland's Stuðlagil, also known as Basalt Column Canyon, is one of the world's most underrated treasures. Often overlooked in favour of the island's better-known attractions, this spectacular gorge is Iceland's best-kept secret. The canyon was formed when a powerful glacial river pushed its way from the highlands to the north of the island, cutting through ancient volcanic rock as it went. The results, we're sure you'll agree, are out of this world.