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

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

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

This crumbling folly looks like an enchanted left over from Middle Earth.

Besieged by war, this castle ruin has crumbled into a peaceful picnic spot.

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

A verdant 17th-century-style garden hidden along Edinburgh’s Royal Mile.

The ruins of an 11th-century Norman castle with a rare, perfectly circular shape.

This unique bridge curls up like a caterpillar to let boats pass and then unfurls again to span a small canal.

A familiar otherworldly creature guards this 12th-century Scottish abbey.

These ancient sunken lanes were naturally tunneled into the soft ground by countless footsteps.

A 6th-century stone lies at the site of the mythical battle waged between King Arthur and his nemesis Mordred.

A metal tree emits eerie, melodic notes on top of Lancashire's Crown Point.

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

The heads of two giant mythological water horses honor Scotland's horselord past.

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

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

A rocky sea serpent hides caves, blowholes, and a spectacular natural bridge.

A subterranean playground in an abandoned slate mine.

At high tide this strange footbridge appears to have no purpose whatsoever.

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

A unique waterfall that some believe attracts the fairfolk.

Accessible only at low tide, the deserted island is dotted with World War II ruins.

Now famous as the "Harry Potter bridge," this impressive concrete viaduct has long been an icon in its own right.