This otherwise innocuous bodega was once the headquarters of the most feared assassin's guild in American history.

Residents of this Brooklyn neighborhood may be unaware their houses sit atop a buried trolley graveyard.

Built as a gift to the hottest tastemaker of the time, these hidden quarters remain an Art Deco showpiece.

The place where Dvořák composed some of his most famous works.

One of the few remaining American elm trees in New York’s Tompkins Square Park was the birthplace of a new religion.

Salute the leader of the proletariat.

Monument to a forgotten NYC disaster that claimed the lives of 1,000.

This former crime corner has been turned into an eclectic community center.

Hidden in one of New York's oldest subway stations is the final remnant of the site of the bizarre Shakespeare Riots.

An 1883 schoolhouse now home to collective of artists.

Two community gardens under the elevated subway lines on a very busy commercial strip in Bushwick.

This 220-year-old house is a reminder of New York City's Dutch past.

This narrow shop in the East Village hosts a matchmaking service for the new millennium.

This exemplar of modernist architecture is meant to captivate and inspire students of the Cooper Union.

The site of the deadly Triangle Shirtwaist Factory Fire.

A living archive of urban activism and space reclaimed.

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

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

Spiral-bound community recipes and antiquarian gems mingle at this small East Village shop.

A hidden "place of interment for gentlemen."

Four cars from the old system were once on display, but were removed in 2014.

Headquarters of the world's fourth largest Hasidic sect and the first of many "770s" around the world.

Historic Greenpoint theater, turned roller disco, now housing a chain pharmacy store.

Home to first responders to Greenpoint's devastating oil fires.