Monty Python fans will recognize this abandoned mine as the Cave of the Killer Rabbit of Caerbannog.

A Victorian Gothic masterpiece housing a world-class collection of rare books and manuscripts.

Museum about life, death, and cannibalism in the Stone Age.

A network of concealed passageways lies within a busy London Underground station.

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

This medieval sanctuary's tree-framed door looks like a portal to a mythical realm.

A closed London rail station created to cart away the dead still bears the marks of attempts to make it less morbid.

A subterranean playground in an abandoned slate mine.

A Victorian natural history and ethnographic museum with wonderful turn-of-the-century, science-book-esque evolution displays.

Surreal riveted sea forts once protected the Kent shores from German attack.

A fantastic castle rumored to be the birthplace of King Arthur.

The signs of a long buried road can still be found hidden beneath a London sewer grate.

This tangled English forest looks like something right out of a fairytale.

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

Northern Ireland's Brobdingnagian stepping stones.

The atmospheric road was never meant to be so creepy.

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

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

An easily overlooked stretch of ornate window fronts and gaslight lamps that could be right from the pages of Dickens.

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

These quintessentially English stepping stones were built for Victorian tourists.

A sacred site for Native Americans surveyed by George Washington and owned by both King George III and Thomas Jefferson.

An array of ancient artifacts from Bronze Age Bristol and other civilizations are housed in this museum.

The mysterious, fantastical woodland inspiration for "The Lord of the Rings."