This ruined medieval castle was the scene of Lord Robert Dudley’s seductive reception for Queen Elizabeth I.

This early Norman castle was the first historical monument protected by an act of Parliament.

These crumbling foundations are all that remain of the once-stately 1840s manor that gave the town of Bradenton its name.

The ruins of this Dutch castle sit atop a labyrinth of once-secret tunnels and passageways, dating back over 900 years.

These ancient symbols freckling a Scottish cliff remained hidden for centuries.

Forgotten jail cells beneath this Scottish town hall are now used for delightfully artful storage.

An optical Illusion once believed to be an electrical phenomenon.

Wonderfully preserved Victorian factory, complete with a preserved steam powered engine house.

This modern labyrinth lies in the shadow of a ruined medieval castle.

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

The curios of pharmacist and collector Henry Wellcome.

This collection of illusory paraphernalia has been culled from the history of London's premier magician's club.

Stockholm's deepest subway station is also a stunning ecological wonder.

A quiet, semi-secret square with statues of Mahatma Gandhi, Virginia Woolf, and a conscientious objectors stone.

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

The enormous 250-room Vanderbilt mansion conceals hidden doors and secret passageways.

A rugged lava field dotted with molds of the ancient pines that were growing when the volcano erupted.

The short-lived railroad town in central Oregon has been abandoned since the 1930s.

10,000 flowered plants bloom in the City of Roses.

The park preserves a single, rare species of carnivorous plant that spells doom for unsuspecting insects.

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

A rare opportunity to drive across the ocean floor.

Take a sea tractor to the Art Deco hotel on the island that inspired Agatha Christie.

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