A morbid secret lies hidden within the beautiful walls of the Boston Athenaeum.

Two thousand artifacts from around the world collected by one woman who loved to travel.

A beautiful Victorian-era cemetery, complete with a miniature village.

This Boston medical museum features the skull of the famous medical case of Phineas Gage.

This historic patch of real estate offers a glimpse of colonial Boston.

Some 2,000 carvings show this rare desert spring has been an oasis for travelers for over a thousand years.

Oxford University's stateliest library seems designed to make students truly feel the weight of knowledge.

A beautiful ruin of a 14th-century Plantagenet castle built by a medieval mercenary.

Long-secret natural history museum, featuring the skull of a "Terror Bird."

In 1943 the British military took control of this village, telling residents they had to leave temporarily. The villagers were never allowed to return.

The biggest and deepest Cold War bunker open to the public can be found in southeast England.

Built by the patron saint of illusionists this Elizabethan manor house is riddled with secret cubbies for hiding priests.

The curious and tiny collection contains some very odd objects.

A Roman spa buried deep beneath the City of London.

There's a labyrinth of medieval chambers hidden deep below a 15th-century pub.

Home to the most complete dodo remains known - one head, and one foot.

A flourishing garden with pigs, donkeys, goats, rabbits, guinea pigs, chickens, ducks, and sheep.

Ancient Egyptian wigs, South American feather headdresses, a bounty of anthropological artifacts in Oxford.

This mysterious underground cave in Shropshire dates back to the 18th or 19th century.

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

Local legends say that fairies used to dance in the moonlight here and invite handsome young men into their grottoes.

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

Cliffs full of fossils at the portal to England's Jurassic Coast.

Art Deco and “Wrenaissance” mash-up, this recently restored royal residence has been home to kings and comes with secret monkey passages included.