Peek inside hidden New York this weekend

New York City doormen and velvet ropes keep snoopers at bay -- except this weekend, when hundreds of buildings and architectural sites, many closed to the public the rest of the year, open their doors for the ninth annual Open House New York.

Peek into the American Irish Historical Society mansion on the Upper East Side, or Eero Saarinen's swooping TWA Terminal at JFK International Airport. Win a prize by photographing yourself in front of architectural landmarks in the Docomomo U.S. Modern Architecture Scavenger Hunt. (For rules, starting at 5 p.m. Friday, log on to docomomo-us.org)

It's all free, but an "OHNY Passport" ($150, tax-deductible) will allow you and a guest to cut to the front of lines at any sites that don't require reservations (visit ohny.org for more info). Here are some highlights of the weekend:

1. DUANE STREET LIVE/WORK LOFT

WHAT Architects Sandro Marpillero and Linda Pollak converted this 1860s industrial building into a hip downtown home/studio, where they now live. Check out state-of-the-art details like the hybrid bookshelf-stair and reflective-surface courtyard.

WHEN | WHERE Sunday, tours every half-hour from 1-4 p.m., 132 Duane St. (at Church Street)

2. LITTLE RED LIGHTHOUSE

WHAT The architect is unknown, but Hildegarde H. Swift wrote the children's book that made this 1880 lighthouse so popular there was public outcry when the city wanted to tear it down. Its lights helped navigate ships before and after construction of the George Washington Bridge, which towers nearby.

WHEN | WHERE Sunday, noon to 4 p.m. Fort Washington Park (enter at the 181st Street footbridge over West Side Highway)

3. NITEHAWK CINEMA

WHAT A former two-story Williamsburg warehouse morphed last year into a sleek cinema with zinc-panel facade, 2,000 hand-cast glass disks backlit by low-voltage LED lights and three new residential floors up top.

WHEN | WHERE Saturday and Sunday, 10 a.m. to noon (architect-guided tours every half-hour), 136 Metropolitan Ave., Brooklyn

4. EAGLE STREET ROOFTOP FARM

WHAT From herbs and jalapeNos to heirloom tomatoes, you name it, it's likely growing (or being planted) three stories up. This 6,000-square-foot organic veggie farm sits atop a Greenpoint warehouse, with a grand view of the Manhattan skyline.

WHEN | WHERE Sunday at 10 a.m., 11 a.m. and noon, 44 Eagle St. (between West and Franklin streets), Brooklyn

5. BOWNE HOUSE

WHAT Quaker and religious freedom advocate John Bowne settled in Flushing about 40 years after the Pilgrims landed. Built in 1661, his Anglo-Dutch-style house is one of the oldest in the city, and full of outstanding period furnishings.

WHEN | WHERE Saturday and Sunday, 2:30 to 4:30 p.m. 37-01 Bowne St. (at 37th Avenue), Flushing