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

Abandoned railway line circling the city of Paris.

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

Medicinal spa created with the discharge from a geothermal energy plant.

This iconic L.A. bookshop is housed in an abandoned bank—both symbolic and chic.

The intricate stonework of Machu Picchu serves as a testament to Incan engineers.

Though its celestial ceiling is impressive, the true star is the vast collection of French books.

New York's oldest and possibly grandest keeper of books.

One of the last Jazz Age "Wonder Theaters" in New York City.

The world’s oldest and biggest bookstore stocking only mystery, crime fiction, espionage, and thrillers.

An unassuming secret door once led to a legendary watering hole.

A legendary speakeasy bookstore returns from the brink.

A Pythagorean funhouse that tries, successfully, to prove that math is the coolest thing ever.

This lower Manhattan bar is set up in an old bank vault that rests beneath a skyscraper that hides even more historic splendor.

A treasure trove of artifacts, books, and artwork from the "golden age" of exploration.

La Monte Young and Marian Zazeela's "Dream House" will immerse you in an ever changing world of sound and light.

A statue marks the exact spot where The Boy Who Never Grows Up made his first literary appearance.

An artistic tribute to the famous singer, just around the corner from where he was born.

Hidden behind a wall for decades, this masonic lodge was only rediscovered during renovations.

The world's first underground farm is in a World War II bomb shelter beneath the streets of London.

Several plaster noses are hidden in plain sight around London's Soho neighborhood.

A mysterious artist-run cabinet of curiosities and library.

London's creepiest cemetery was once the site of dueling magicians and mobs of stake-carrying vampire hunters.

A contemporary fresco movement illustrates the region's rich history.