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

Exquisite wall sculptures carved in secret by an early quarryman in an obscure corner of the Paris Catacombs.

One of the greatest maze designer’s greatest mazes.

An overlooked marble is the only surviving in-place 18th century example of the measurement that changed how we define distance.

This Parisian café sticks almost exclusively to an ethos of reuse.

19th century pendulum and a clock restored by a rogue group of guerilla artists.

"In the Dark" Restaurant in Paris offers dinner in complete darkness.

France's national museum of scientific and industrial instruments.

This whimsical castle of grottoes was the labor of love of a French postman, and one of the greatest achievements of outsider architecture.

A surrealist timepiece by the artist of melting clocks.

A scandalous Art Nouveau collaboration that set Paris all atwitter at the turn of the century.

This iconic Parisian bookstore doubles as the "Tumbleweed Hotel" for traveling writers.

Paris' linguistic guide to the international language of, yes, love.

This massive library holds what was once the largest book collection in the world.

The macabre collection of Jacques Sirgent, an expert scholar on the undead and all of their trappings.

The vast, legendary catacombs hold secrets much stranger than stacked bones.

This massive blockhead sculpture hides an entire library.