The library of every book lover's dreams.

Cryptic messages embedded in the New York City sidewalk.

This plot of old-growth forest is the largest surviving remnant of New York City's original woodland.

An annual extravaganza of Broadway theater memorabilia.

In upstate New York, gorgeous waterfalls and a watermill are slowly being reclaimed by nature.

Neon signs that grace the windows of Bergdorf Goodman's and Tiffany & Co. come from this studio in Brooklyn.

The oldest bibliophilia club in America, with exhibitions on historic books and graphic arts.

A bit of retro transportation flair preserved in the world's largest department store.

An uber-secure, windowless tower of doom in the center of Manhattan is an NSA spyscraper.

The beautiful tunnel that ran from the lobby to Penn Station is still hidden underneath 34th Street.

Unique antiquarian shop specializing in globes, maps, and prints.

The world's oldest hologram gallery and the labyrinthine laser laboratory of a holography pioneer.

This former Norwegian sailor's church is slowly being taken over by ramshackle robot musicians.

The oldest family-run luncheonette in New York, last renovated in 1948, still serves food and drinks the old-fashioned way.

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

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

Amid the bustle and noise of the Financial District hides a secluded garden oasis above the city streets.

Nondescript elevator doors open to reveal a stunning, surreal world.

A three-story copper skybridge connects two Manhattan buildings with Art Deco luxury.

More gold than anywhere else, ever.

Nikola Tesla's former home contains an homage hidden from plain sight.

New York City's smallest piece of private property.

A stunning, two-tiered waterfall made famous by poets, artists and the legend of a ghost dog.

Whisper secrets in a busy station only to be heard on the other side of this acoustic arch.