A discreet little stairway on St. Nicholas Avenue leads to a quaint and unexpected cobblestone street of 19th century wooden rowhouses.

Little Red Lighthouse under the George Washington Bridge.

Three-story slide through the New Museum.

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

The oldest surviving bridge in New York City, which reopened to pedestrians in 2015.

Read a book next to a Midtown waterfall.

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

Elevated freight railway turned wildly successful urban park.

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

Rome's ancient Etruscan rival, now a park full of ruins.

One of seven Jewish catacombs in Rome and one of only two open to the public.

The engineering wonder and pleasure dome of a much-maligned emperor still holds undiscovered secrets.

The only "Egyptian" pyramid in Europe and the legendary tomb of Remus.