There's a 12-foot-tall replica of the Washington Monument hidden under a manhole nearby.

A tiny piece of the Moon is embedded in this stained glass masterpiece.

A wondrous old library overlooking the nation's capital.

A historic neighborhood church is reborn as a psychedelic arts collective.

Long-abandoned trolley tunnels just a mile away from the White House are turning into an art space.

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

The United States Capitol's former columns still stand.

A steampunk-styled three-floor factory churning out art, activism, and electronic beats.

A museum dedicated exclusively to the lore and history of ouija boards.

This historic address is home to the beloved ball and is an almost totally empty building among the most expensive real estate in the world.

A beautiful collection of architectural ornaments rescued from demolished New York City buildings.

This outdoor gallery of graffiti-covered walls pays homage to the past, present, and possible future of street art.

A curious fountain that has no water and includes Satan, a crab, and 9 giraffes.

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

This small, hidden cove is home to abandoned boats.

You can still ride this 100-year-old work of art in Brooklyn's largest public park.

A hyper-luxurious, 12,000- square foot home might be buried beneath Queens, still waiting to protect you from nuclear missiles.

A clock set into the concrete outside a Manhattan jeweler has been telling time underfoot for over a century.

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

The end of the 4 Line is also the end of the line for 300,000 souls in one of NYC's most illustrious cemeteries.

An oasis of calm amid the chaos of the boardwalk, the museum traces the heritage of this beloved beachside amusement park.

Detailed facade of a brownstone in Boerum Hill.

From scholastic to sepulchral - now under reconstruction.

The remnants of two World's Fairs are here, complete with a 12-story globe, a mini-Manhattan, and a UFO-shaped pavilion.