The 2,000-year-old Roman columns are hidden within Barcelona's Gothic Quarter.

A beautiful but toxic fountain of mercury.

This semi-secret storybook hedge maze is also the oldest garden in the city.

A book bound in the skin of an infamous criminal, along with countless other specimens.

Hidden in a Scotland museum is a copse of extinct tree stumps.

This Scottish museum is the only one in the world to focus not on one religion but all of them.

A book collector's dream, this Toronto bookstore has the world's first "Biblio-Mat," a random book vending machine.

Walking by this fence is like strolling along a portal to various fictional worlds.

Sniff the Titan Arum's rotting flesh.

This wall on a street corner in Lower Manhattan has been a blank canvas for a rotation of renowned artists since the 1980s.

An artist's cute bronze subway sculptures belie his violent artistic past.

A Manhattan courthouse hides a small but scathing memorial to Holocaust injustice.

Manhattan's lighthouse, erected at the insistence of the unsinkable Molly Brown.

The oldest house in Manhattan is now a museum that remembers the home's sordid history of scandals, vice-presidents, and ghosts.

Blighted Irish field and the ruins of a 19th-century cottage on the edge of urban Manhattan.

Hidden in Central Park's Ramble is a troublesome cave buried just beneath the surface.

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

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

Manhattan’s Battery Park has a whimsical carousel full of spinning, glowing fish.

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