Open up, New York! Annual tour takes you behind the scenes

A sewage treatment plant. A crypt containing the remains of Revolutionary War POWs. A federal Superfund toxic waste site. A really old church.

These are just some of the highlights of the Brooklyn portion of the annual “Open Space New York” tours of super-secret locations typically closed off to visitors.

There’ll be more than 300 sites citywide during the two-day event next weekend — some viewable for free, others for $5.

“We open up sites in all five boroughs educating people about architecture, design and cultural heritage; these are spaces you walk past every day, but don’t know what’s behind the doors,” said Open House New York Executive Director Renee Schacht.

Root with a View: Take a tour of the Eagle Street rooftop farm at Open House New York on Oct. 15 and Oct. 16.

Photo by Scott Nyerges

Here are the coolest sites in the County of Kings:

Christ Church

Brooklyn’s oldest Episcopal church, designed by Richard Upjohn, features early English and perpendicular Gothic architecture from the 1840s.

Christ Church (320 Clinton St. at Kane Street in Cobble Hill), Saturday, 10:30 am-12:30 pm; and 1:30-4:30 pm.

Eagle Street Rooftop Farm

Who says you can’t be urban and agricultural at the same time? Pay a visit to this rootop greenspace, a 6,000-square-foot vegetable garden on top of a warehouse on the banks of the East River — trust us, the views from up there are breathtaking.

Want to see some bubbling sewage? You’re in luck! Greenpoint’s very own wastewater treatment plant “digester eggs” will be open for tours during Open House New York on Oct. 15 and Oct. 16.

Photo by Walter Dufresne

Eagle Street Rooftop Farm (44 Eagle St. at West Street in Greenpoint), Sunday, 10 am, 11 am, noon.

Pratt Institute’s Myrtle Hall

The new Myrtle Hall, a six-story, 120,000-square-foot green academic and administrative facility on Pratt Institute’s Brooklyn campus is a LEED Gold building featuring sun shades, a green roof and solar photo-voltaic panels.

Myrtle Hall (536 Myrtle Ave. at Grand Avenue in Clinton Hill), Saturday, 1 pm, 2 pm, 3 pm with Richard Scherr, director of Facilities Planning.

Myrtle Hall at Pratt Institute, a a six-story, 120,000-square-foot green academic and administrative facility on Pratt Institute’s Brooklyn campus, will be open for tours during Open House New York on Oct. 15 and Oct. 16.

Photo by Alexander Severin

Franke, Gottsegen, Cox Architects

Stop by this former garage turned striking two-story architectural studio with soaring interior space and a charming walled garden.

Franke, Gottesegen, Cox (78 Union St. at Colombia Street in Red Hook), Saturday and Sunday, 10 am-4 pm.

Gowanus Canal Sponge Park

Learn all about an open space system that remediates surface water runoff while also adding accessible urban open space to underserved neighborhoods. This design uses landscape, architectural and engineered strategies to help make waterways cleaner by slowing, retaining and filtering storm water.

Sponge Park (Fourth Avenue at Degraw Street in Gowanus), Saturday, 11 am.

Tours from the Crypt: The Prison Ships Martyrs Memorial in Fort Greene Park will be open during Open House New York on Oct. 15 and Oct. 16. Inside are the remains of 11,000 victims.

Photo by Sebastian Kahnert

Lott House

Get a behind-the-scenes preview of the partially restored Dutch Colonial home of Hendrick Lott, plus some archaelogical discoveries. Don’t miss it; this exhibit is so new it’s not even open to the public yet.

Lott House (1940 E 36th St. between Filmore Avenue and Avenue S), Saturday and Sunday, 11 am-3 pm.

Lefferts Historic House

Built by a Dutch family in the 17th century, the Lefferts homestead is one of the few remaining farmhouses from colonial Brooklyn and features original timber framing, period decor and remnants from a neo-Classical remodeling.

Lefferts Homestead (452 Flatbush Ave. between Empire Boulevard and Grand Army Plaza inside Prospect Park), Saturday and Sunday, noon-5 pm.

Park it in the Park: The Lefferts Historic House in Prospect Park will open its doors to visitors for Open House New York.

Nitehawk Cinema

Who doesn’t love going to the movies? Especially if you can meet the architect who designed this theater-restaurant!

Nitehawk (136 Metropolitan Ave. at Berry Street in Williamsburg), Saturday and Sunday, 10 am-midnight.

Pier Glass Art Studio + Scanlan Glass

Visit a Civil War-era warehouse sitting on the Bay of New York Harbor, with a killer view of the Statue of Liberty. What could be cooler? Oh yeah — it’s also a glassblowing studio.

Pier Glass (499 Van Brunt St. in Red Hook), Saturday, 10 am-7 pm; and Sunday, 10 am-5 pm.

Take a tour of Christ Church in Cobble Hill — the oldest Episcopal church in Brooklyn!

Pieter Claesen Wyckoff House

The city’s oldest home — and first landmark!

Wyckoff House (5816 Clarendon Rd. between E. 58th and E. 59th streets in Flatbush), Saturday, 1 pm, 3 pm; and Sunday, 11 am, 1 pm, 3 pm.

Prison Ship Martyr’s Monument

More than 11,500 men, women, and children died on British Prison Ships in the Revolutionary War and their remains buried in a crypt under Fort Greene Park. Spooky? Yep, but a rare chance for you.

Martyr’s Monument (inside Fort Greene Park between Dekalb and Myrtle avenues in Fort Greene), Saturday and Sunday, 11 am-3 pm.

Farming in Flatbush: Check out the Pieter Claesen Wyckoff House and learn about Brooklyn’s agrarian past!

Visitor Center at Newtown Creek Sewage Treatment Plant

Don’t miss the opportunity to take a tour of the city’s largest wastewater treatment plant — eight stainless steel digester “eggs” on the banks of Newtown Creek. Highlight: watching sewage bubble through a plastic porthole (but not smelling it!).

Newtown Creek Wastewater Treatment Plant (329 Greenpoint Ave. at Humboldt Street in Greenpoint), Saturday and Sunday, 10 am-2:30 pm. No strollers.

Open House New York runs Oct. 15 and Oct. 16. For info, call (212) 991-6470.