Hundreds of hidden passageways weave through the old quarters of Lyon.

This futuristic observatory at the top of the Pyrénées offers unrivaled views.

A chapel on a volcanic core, marking the end of a successful journey.

The shape of this old salt factory complex was inspired by the course of the Sun.

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

This 17th-century street hidden beneath Edinburgh was once a breeding ground for the black death.

A 18th century graveyard and its astonishing cortege of macabre iconography.

One of the oldest scientific gardens in Britain, containing more than 13,302 plant species in its core collection.

Ruined 11th century abbey built by King David I in Edinburgh, Scotland.

Each spring this woodland floor is carpeted with purplish flowers as far as the eye can see.

William Blake claimed to have painted this gothic masterpiece after encountering this nightmarish being in a vision.

Islanders once used this dramatic, otherworldly landscape to hide their cattle from Viking raiders.

An small and easily overlooked archaeology museum chock full of Egyptian artifacts.

The curios of pharmacist and collector Henry Wellcome.

English antique dealers with a taste for the unusual.

Historic church where a number of Shakespeare's actors are buried.

A clock designed to run with perfect accuracy for 10,000 years.

Abstract dinosaur models in London.

Winding paths and ramshackle mausoleums in the oldest "park cemetery" in London.

A friendly pub with a sordid past in cock fighting.

The John Snow Memorial marks the epicenter of London's 1854 cholera epidemic.

The barrel-made lookout from Shackleton's final ship is tucked away in the crypt of one of London's oldest churches.

Gothic tower where Lord Alfred Tennyson wrote the poem "The Sleeping Beauty."

The oldest surviving glass furnace cone in Western Europe.