Decades after testing the polio vaccine on unwitting patients, this historic mental hospital sits in ruin.

The name of this famed hospital was once a byword for the horrors of medical and psychiatric care.

This little-known collection holds everything from "Dracula" notes, to the manuscript of "Ulysses," to the forged works of Shakespeare.

During the 19th century, you could pay for violence off a prix fixe menu on this Manhattan street.

The second-largest (of only two in the world) large particle collider is the underdog of experimental physics.

A miniature rainforest is growing inside of a Midtown Manhattan office building.

This hidden library of physiological ephemera contains centuries worth of knowledge on the vim and viscera of the human body.

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

This semi-secret garden in south Seattle emulates a traditional Japanese garden using the plants of the Pacific Northwest.

A pair of pure white felines guard the entrance to a spot of California real estate established as an artist's haven.

At 135 years old and counting, this historic print shop is heaven for poster nerds and music buffs.

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

In its day this historic fort held 100 cannons pointed in almost every direction to protect New York.

America's greatest forgotten garden and the former stomping grounds of Son of Sam.

The feral felines of Roosevelt Island have a small army of allies and an abandoned hospital all to themselves.

Tucked away amidst some of the most famous addresses in the world is New York's only fraction of a street.

A crumbling hospital from the 1850s on Roosevelt Island.

A tiny museum housed in a New York freight elevator specializes in the "overlooked, dismissed, or ignored."

A museum devoted to bringing to light forgotten or neglected histories through exhibitions, education and public programming.

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

Three hundred years of preserved Spanish colonial history in San Antonio.

Continuing the tradition of the dime museum in style.

This neon blue river gets its color from a unique mix of bacteria and volcano minerals.

A house filled to the brim with oddities and curiosities.