A modern mechanical planetary system, part of a 10,000 year clock.

The only theatre in the world constructed specifically for sound movement.

One of the oldest producers of hand-folded fortune cookies still uses its original secret recipe.

The tea room that pushed the boundaries of adorable straight into...we can't find the words.

A winding path built in secret on the edge of the continent.

A tiny theater hidden in an alley plays a constant stream of short silent films for anyone willing to peer through the peephole.

A 140-year-old castle with underground caves hidden in San Francisco.

In all of the 29 years it was in operation, no prisoners ever escaped successfully... or so they claim.

Bring your own cardboard to the slippery slopes of concrete hidden in a neighborhood park.

An artsy hidden staircase leads to breathtaking views of San Francisco.

A psychedelic labyrinth on the San Francisco bay.

A huge musical instrument played by the ocean.

This ruined fort hidden at the top of Central Park can't seem to keep from losing its historical plaques.

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

The superstar of Cold War nuclear bunkers has been featured in countless films but is now barely operational.

The longest navigable underground river in the United States is home to countless blind and albino animals.

The skull of the patron saint of lovers lies in the Basilica di Santa Maria in Cosmedin—maybe.

The doodles of a genius line the walls of a secret room under the Medici Chapel, where they were hidden for nearly 500 years.

Originally conceived as part of a proposed Arizona State Capitol building in the 1950s, this structure built in 2004 stands as a monument to the architect's legacy.

Become a prohibition rebel.

New York City's only radical feminist independent bookstore.

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

During the holidays, a vintage subway train whisks New Yorkers back in time.

A special area of the National Archaeological Museum of Naples is located inside a metro station.