Under a church hides a forgotten 13th-century ossuary containing the remains of around 2,500 people.

This quaint mortuary chapel hides a stunning Celtic Revival and Art Nouveau interior.

This hidden natural fountain issues forth a steady supply of supposedly healing water that tastes like rotten eggs.

This Gothic Revival castle used as a shooting location for "The Secret Garden" and other films.

The largest known medieval map of the world.

This logic-defying 16th-century Tudor manor still stands to the delight and astonishment of onlookers.

An English artist has turned an unassuming ex-council house into a time-lost house of mystery.

Dating back almost 400 years, the oldest public collection library in the United Kingdom was once the study hall of Karl Marx.

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

The oldest inn in England served brew to the crusaders.

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

A modern English garden of eccentric beasts, follies, and oddities.

Mysteriously stacked storefront paths give this medieval British town an iconic style like none other.

A church that bred legends, and served as an inspiration for the Da Vinci Code.

The curios of pharmacist and collector Henry Wellcome.

Amazing and mysterious Neolithic settlement on Scotland's Orkney Islands.

A subterranean ice warehouse that has lain hidden beneath central London for over a century is now open to the public.

This London pub hides a peculiar secret: a recreation of the rooms shared at 221b Baker Street by Sherlock Holmes and Dr. Watson.

17th century streets hidden under Edinburgh were once a breeding ground for the black death.

The popularity of Sherlock Holmes led to the creation of his fictional address, turning the orderly London street numbers askew.

Northern Ireland's Brobdingnagian stepping stones.

The hidden "ballroom" under a mansion lake was built by a criminal who ate a cyanide pill during his trial.

The world's largest collection of witchcraft regalia.

A kaleidoscopic warehouse-maze of handmade neon signs.