This English medieval castle is where King John died of dysentery.

This restored 17th century "conduit house," often mistaken for a watchtower, actually supplied water to nearby Bolsover Castle.

This shop and gallery is a modern-day cabinet of curiosities, unassumingly positioned along an urban thoroughfare.

A Roman spa buried deep beneath the City of London.

This legendary stone is of unknown origin, and throughout history has been a literal touchstone for British leaders.

Rebuilt remains of a temple to Roman god Mithras.

Buried for centuries, this hidden cellar is all that remains of London's medieval Whitefriars Monastery.

The whimsical twist of this spire was either caused by the Devil, an unexpected virgin, or lead.

An unusual round church in London with a Templar past.

Victorian-era Londoners really wanted to believe this 17th-century cistern was actually an ancient artifact.

Since 1874, this macabre collection has developed into a museum devoted to Scotland Yard's mementos of dastardly deeds.

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

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

The remains of the great moral philosopher reside in a university in London.

Hauled from the water's depths, Henry VIII's flagship is preserved in this capsule-shaped museum.

A mysterious demonic figure peers down from its perch within the gorgeous Chester Cathedral.

Western Europe's only representation of a Roman goddess still in its original location sits in an unassuming park.

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

This mysterious hilltop collection of Druid carvings isn't quite what it seems.

The world's largest prehistoric copper mine had 30,000 animal bones scattered throughout the maze of passageways.

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

The remains of the oldest synagogue in Britain lay forgotten for seven centuries, hidden under a humble shop.

A reportedly haunted 14th century church is curiously facing the “wrong direction.”

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