This free, take-a-book shop seems like a trick but isn't.

A hidden alley in urban Baltimore is a haven for graffiti artists.

An "inside out" building in the historical center of Paris, featuring Europe’s largest modern art museum.

The first green space constructed on an elevated viaduct.

A mysterious air force base built to resemble a Long Island fishing village.

Not merely a museum – but a whirring powerhouse that offers a subterranean peek into the heart and soul of cable car operations.

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

A world-class collection of mechanical musical instruments and automata.

Once America's longest-manned military fort, now an abandoned hulk.

One of the most enjoyable bits of history at Coney Island and “the most romantic ride in the world.”

A former seaside jewel built for the everyman is now simply a neglected art deco fortress.

Empty, but not abandoned, this cavernous Brooklyn loading dock was once considered the largest individual building in the world.

A Victorian cemetery in the heart of Brooklyn remains a popular mecca of morbid curiosity.

One of only two remaining Victorian-era greenhouses in New York.

An unconventional space for art and science housed in a massive old warehouse.

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

Elevated freight railway turned wildly successful urban park.

Love, knishes, and best wishes from this legendary Lower East Side bakery.

A no-frills cinephile haven known for showing offbeat, underseen films.

A notorious punk house turned co-op.

The home of one of America's most beloved fictional characters has become a real world landmark.

Once a ferry dock, radio transmitter, and now a new Greenpoint park.

One of New York's best collections of pinball is hidden in a secret bar in the back of this laundromat.

The factory for the popular Dumbo location, the Greenpoint shop is a quiet gem.