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

A charming 17th-century alley is lined with secondhand bookstores and antiquarian shops.

This massive collection of British military artifacts includes the heartbreaking personal letters of the men in the trenches of WWI.

The sixth of London's "Magnificent Seven" cemeteries, and a source of unlikely inspiration to Beatrix Potter.

Once thought to be the mysterious work of a witchy prophetess, a well with unusual properties turns objects into "stone".

The one-time stronghold of the noble Douglas family, now home to ghost sightings and nesting birds.

The ruins of this gorgeous clifftop castle look like something from a fantasy novel.

Scattered throughout London are ancient remnants of the city's former bounding wall.

A unique waterfall that some believe attracts the fairfolk.

The fountain marks the area where hundreds of accused witches were burned at the stake.

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

A 18th century graveyard and its astonishing cortege of macabre iconography.

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

This series of Scottish caves has no clear purpose other than baffling historians.

Remnants of a Victorian garden feature sitting in public woodland.

A island reachable by a causeway at low tide is possibly one of the earliest Western European locations to be identified in text.

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

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

This castle was established by the 4th Duke of Montrose and is connected to the Buchanan Clan.

A 1,215-foot tunnel transports pedestrians beneath the River Thames.

A vast overgrown cemetery, once known as one of London's "Magnificent Seven."

Ruined 11th century abbey built by King David I in Edinburgh, Scotland.

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

An unusual round church in London with a Templar past.