France's national museum of scientific and industrial instruments.

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

This recipe is set in stone.

This massive subterranean fissure is known as the "underground Grand Canyon."

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

This Parisian fountain is a little bit fantasy and a little bit nightclub.

A subterranean shelter remains intact under a busy Paris railway station.

Medieval museum built over Roman baths that features famous tapestries of a lady and a unicorn.

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.

A surrealist timepiece by the artist of melting clocks.

A favorite Paris bar for U.S. expats, including Gershwin, Hemingway, and James Bond.

A counter-culture bookstore like no other hides in plain sight in the streets of Paris.

The very center of Paris is surrounded by a bevy of strange good luck rituals.

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

High atop the Eiffel Tower is a small apartment built exclusively to entertain the science elite and make the rest of Paris jealous.

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

Hidden in a grotto 26 feet below Nottingham's oldest hotel, this stylish subterranean drinking den is notoriously hard to find.

The gravestone of a delicate singer-songwriter bears a fittingly introspective epitaph.

An easily overlooked stretch of ornate window fronts and gaslight lamps that could be right from the pages of Dickens.

Drink wine handed out through a window as part of an age-old tradition.

A 16th-century horror show built in a lovely Italian garden.

This quaint Italian town keeps losing ground as the sides of its plateau slowly erode.

This picturesque Umbrian city has a subterranean side that has long remained hidden.