San Francisco's most expensive hotel suite includes a secret passageway rumored to have been used by JFK.

A pair of slides and a tree-lined stair corridor have been an urban oasis for nearly 40 years.

A museum befitting the city responsible for supplying the majority of the world's LSD.

A museum on the history of Paris, including a set of Napoleon's toiletries, Proust's room, and relics of the Revolution.

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

The floorboard scrawling of a tragic madman is on public display outside a Paris hospital, much to the dismay of its opponents.

Natural history museum celebrating biodiversity with a parade of taxidermy animals.

A modern-day Lascaux cave underneath Paris.