One of the few standing Roman lighthouses and a labyrinth of tunnels are a couple of the secrets at this historic castle.

The ghosts of Britain's telecommunication past sit rusting away in a small village in England.

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

A hermit's tiny cell built into the cliffside that saved him in South Pembrokeshire.

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

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

A giant pineapple, a symbol of hospitality, and an amazing vacation rental option.

This short bridge is the only thing connecting a tiny Irish island to the mainland.

Eyam took steps to quarantine themselves and keep the plague from spreading.

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

A petite castle folly in the English countryside.

A 200-year-old collection of oddities and medical paraphernalia.

The mystery of this small, brick pond eluded its possibly only investigator until his death.

Claiming to be the oldest hat store in the world, this historic haberdashery had a hand (and a head) in the creation of the Bowler.

Thanks to modern navigational tools we now know that the true prime meridian runs through a park next door.

One of the largest sculpture collections in the U.K. features history's greats, from Bob Dylan to Galileo, in bronze.

Bronze sculpture celebrating the relationship between Churchill and Roosevelt.

The stately remains of Llywelyn the Great's mighty fortress.

This beautiful "lagoon" is actually a toxic soup filled with cars, carcasses, and trash. When warnings couldn't stop people from going for a dip, the town dyed it black.

This small museum in a former church crypt contains artifacts of the Elephant Man, Jack the Ripper and Florence Nightingale.

This iconic 1,000-year-old medieval castle is a favorite of the film industry, most notably as the location for Hogwarts in Harry Potter.

Fantastically decorated underground chambers built in the 1760s.

A house of bones — but nobody is quite sure to whom they belong.

Old-fashioned knowledge and modern engineering create the world's only rotating boatlift.