The sign at the garden gate reads: "These Plants Can Kill."

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

Created hundreds of years ago, the magical follies and landscapes at this park were almost lost to time before being restored.

A unique waterfall that some believe attracts the fairfolk.

This long-distance walking route follows the Prime Meridian line as it passes through England.

A 4,500-year-old forest is slowly being revealed from beneath the sands of a Welsh beach.

A harem-inspired Moorish fantasy design in a Victorian-era Welsh castle.

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

This silent sentry in the crypt below a large Gothic cathedral is often knee-deep in water.

An Oxford museum where visitors can have tea with the Mad Hatter and climb through the wardrobe to a fantasy land.

This magical museum celebrates the life and work of a seminal children's book writer (and occasional spy).

Numberless clock creates a meal of time for the dreaded, insectile Chronophage.

A succession of eerily contemplative iron figures lead from a Scottish museum to the sea.

The taxidermy remains of the first mammal ever cloned from an adult cell are on display in Edinburgh.

Long abandoned underground complex to keep royals safe from a nuclear war that never came.

Protecting the dead from opportunistic body snatchers.

There are plenty of wonderful panoramic vistas in Edinburgh, but not many are hidden smack in the middle of the Old Town.

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

Tiny effigies of the victims of Edinburgh's famous Anatomy Murders.

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

Below a historic English market town lies a secret underground city complete with kitchens, laundries, storerooms, and an underground lake.