This abandoned caretaker's apartment is one of 13 left in the New York Public Library system.

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

The front yard of an Upper East Side town house hides the last fragment of one of New York's most famous theatres.

New York's oldest and possibly grandest keeper of books.

Hidden in Central Park's Ramble is a troublesome cave buried just beneath the surface.

The fanciest public restroom in New York City boasts fresh flowers, art, and a classical music soundtrack.

The famous facade of Grand Central Terminal hides a regulation tennis court, and it's not the first one.

Hidden behind a gate in Greenwich Village is a little farmhouse that once served as the writing studio of a bestselling author.

Cold War intelligence agents monitored communist embassies from an attic in a former pigeon coop.

A mysteriously dark cemetery monument fuels stories and legends galore.

A haunting tribute to pioneering photographer Clover Adams.

With over 100 jam-packed rooms to explore plus elaborate tea services and events, the Mansion on O Street is a hidden treasure.

This grand gothic brewery has been pumping out suds for over a hundred years.

Also known as the Founding Church of Scientology.

Obscure Freemasons still live in D.C.’s largest private residence.

This imposing Masonic temple a mile from the White House was the first public library in Washington, D.C.

Remains of a historic fountain that was mysteriously lost in the demolition of a D.C. traffic circle.

A master of deception, Harry Houdini's greatest trick may have been living in two places at once.

This lonesome Monterey cypress has survived centuries of wind, salt, and at least one attempt at arson.

One poet's handmade, anachronistic home.

Once America’s most beautiful army base, this abandoned military fort on the coast of Monterey Bay has been left to the elements.

A lonely monument to the original Silicon Valley tech campus.

The headquarters of a secretive order is also a beautifully-designed park.

One of the largest Marian shrines on the West Coast stands rather unexpectedly in Silicon Valley.