One of only two commuter aerial tramways in the United States.

New York City's smallest piece of private property.

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

This little museum is built on a theater that was once a wildly elaborate speakeasy.

A hip bar decorated with walls of golden skulls.

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

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.

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

Elevated freight railway turned wildly successful urban park.

Try not to get slimed in Tribeca.

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

This abandoned subway station beneath the Waldorf-Astoria hotel is allegedly used to secretly transport presidents.

Dodge prohibitionists and slide through the telephone booth in Crif Dogs.

This beautiful building in the heart of Manhattan's Financial District was empty for decades.

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 beautiful and abandoned New York subway station from 1904, complete with chandelier.

An eccentric artist's abode in this small Italian town has been transformed into a surreal temple of mosaic madness.

The glowing blue Nymphaeum of Emperor Tiberius.

Harlequin costumes, signed scripts, and armor-wearing puppets.

Ever hear of the Milazzo Cage?

Italy's third-largest Roman arena gives a peek into the underground operations beneath the ancient spectacles.

Italy's "New Mountain" rose from the ground in a volcanic eruption in 1538.