During this Shetland Islands celebration, hundreds of torch-carrying "guizers" lead a procession to burn a viking longboat.

At high tide this strange footbridge appears to have no purpose whatsoever.

An intriguing three-sided folly is a testament to one man's devotion to Catholicism and the number three.

This tiny island featuring 9th-century Viking ruins is only accessible at low tide.

Europe's largest prehistoric mound – burial site of a legendary king?

This tiny little cave was said to have been a refuge for a saint with a glowing arm.

A strange rock with a sinister reputation lurks within the crimson waters of this Scottish glen.

Art Deco and “Wrenaissance” mash-up, this recently restored royal residence has been home to kings and comes with secret monkey passages included.

The Origin of On the Origin of Species.

Hidden in a grotto 26 feet below Nottingham's oldest hotel, this stylish subterranean drinking den is notoriously hard to find.

This antique prison is a tourist attraction with a sordid past.

The barrel-made lookout from Shackleton's final ship is tucked away in the crypt of one of London's oldest churches.

This silent sentry in the crypt below a large Gothic cathedral is often knee-deep in water.

Long-secret natural history museum, featuring the skull of a "Terror Bird."

This one has sailed five times as far as Sir Francis Drake's famous ship.

A secret garden in a picturesque Edinburgh village has inspired artists for centuries.

High Victorian fantasy created a fairytale castle out of a ruined fortress in Wales.

19th century museum with an eclectic mix of curiosities, from Egyptian artifacts to items on archery history to the skull of the world's oldest horse.

This tiny little pool is said to be home to a malicious mermaid named Jenny Greenteeth.

A sweet symbol marks the place where torturous executions were once carried out.

Legend says this cave housed a 16th-century cannibal and his family of 48.

This mysterious underground cave in Shropshire dates back to the 18th or 19th century.

A midnight snack that lights up the night.

The remains of a grand castle that may have inspired Bram Stoker's Dracula.