Open House New York: How To Explore NYC's Hidden Treasures

NEW YORK — Sure, the Empire State Building's famous observatory and Grand Central Terminal's awe-inspiring ceiling are pretty cool. But what about the Cathedral of St. John the Divine, or the Hall of Records, or the inside of the Prison Ship Martyrs Monument?

Those are among the 250 hidden treasures across New York City that will be accessible to the public Friday to Sunday for the 17th annual Open House New York weekend.

The eponymous nonprofit aims to open up fascinating sites across the city that might otherwise go unnoticed by tourists — or even lifelong New Yorkers. The lengthy list includes workspaces, private homes, cultural facilities, municipal buildings and churches.

Visitors can take tours or hear talks from experts at some of the sites, while others will be open to explore on your own. Reservations are required at certain locations, and some are already sold out, but many will let New Yorkers come and go as they please.

The Open House New York website has a full list of all the participating sites and when they'll be accessible. But here are a few highlights of this year's weekend of exploration.

Prison Ship Martyrs Monument
Fort Greene, Brooklyn
11 a.m. to 3 p.m. Saturday
The century-old monument at Fort Greene Park honors more than 11,500 people who died on British prison ships during the Revolutionary War. The tour offers a rare chance to peek inside the structure.

Brooklyn Grange Farm Rooftop
Sunset Park, Brooklyn
11 a.m. to 4 p.m. Sunday
Brooklyn Grange grows more than 80,000 pounds of produce a year at its three rooftop farms across the city. Make sure to wear appropriate shoes for a visit to this working Sunset Park farm.

Hall of Records at Surrogate's Courthouse
Civic Center, Manhattan
10 a.m. to 4 p.m. Saturday
The home of the city's Department of Records and information services is also "a fine example of Second Empire architecture," according to its Open House listing. Visitors this weekend can check out exhibits including the "Central Park Drawings" and "The Language of the City: Immigrant Voices."

East River Compost Yard
Lower East Side, Manhattan
10 a.m. to 2 p.m. Saturday
More than 1 million pounds of compost are dropped off each year at one of the biggest composting sites in Manhattan. Visitors to the 1-acre facility in East River Park should wear closed-toed shoes.

The Church-In-The-Gardens
Forest Hills, Queens
10 a.m. to 2 p.m. Saturday
This still-active church was designed by Frederick Law Olmsted collaborator Grosvenor Atterbury along with John Almay Tompkins. The 1915 building is "dominated by Gothic and Norman influences, with touches of the Romanesque," according to Open House.

GallopNYC Sunrise Stables
Ozone Park, Queens
10 a.m. to 2 p.m. Saturday and Sunday
One of the city's few remaining horse stables was just renovated in 2016. Open House visitors can take a guided tour touching on the site's history, horse therapy programs and horseback riding in the city.