This cramped crevasse saw the entire population of its island suffocated inside its depths.

A local tree surgeon has created a whimsical walk full of carved tree stumps near Scotland's Loch Lomond.

A mysterious monument where a woman who records say never existed was burnt alive for being a witch.

Besieged by war, this castle ruin has crumbled into a peaceful picnic spot.

This abandoned asylum in Wales might look haunted, but it's still beautiful.

This beautiful Victorian ironwork masterpiece was built to keep London from smelling like poop.

A small island abbey is the final resting place of many medieval Scottish monarchs, including the real Macbeth.

This stately estate house features a tower covered in a bright, modern mural.

London's last remaining public soapbox site has seen speeches from Karl Marx, Vladmir Lenin, and George Orwell.

A site of pagan worship which still attracts people looking for fairies.

Below a historic English market town lies a secret underground city complete with kitchens, laundries, storerooms, and an underground lake.

The last inhabitants of one of the U.K.'s most remote islands were evacuated in 1930.

Islanders once used this dramatic, otherworldly landscape to hide their cattle from Viking raiders.

This Scottish bridge seems to compel dogs to leap to their death.

The largest cave chamber in Britain—big enough to fit a whole cathedral inside.

A pagan tradition of draping trees with rags eerily lives on.

Accessible only at low tide, the deserted island is dotted with World War II ruins.

The true age of this ancient stone circle is unknown, but its stunning vista isn't in question.

Shakespeare, David Bowie, Dr. Who, the Saxons, Druids and Romans are all claimed to have all made their mark on these massive man made tunnels.

A clock designed to run with perfect accuracy for 10,000 years.

An ancient Scottish rock formation said to be the gravesite of a giant remains ensconced in legend and intrigue.

A rocky sea serpent hides caves, blowholes, and a spectacular natural bridge.

The decaying ruins of Wales' first asylum for the mentally ill.

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