Astoria actually has the city's largest pool at 330 feet long—that's because it was built as a model for 10 other NYC pools under the Robert Moses administration. It was also used by the U.S. Swim and Diving teams during the 1936 summer Olympic Trials and again in 1964.
There are two fountains at the east end of the pool that spray water 25 feet in the air that were uses as Olympic torches then.
The pool lies in the shadow of the midtown skyline—the RFK and Hell Gate Bridges tower can be seen from here—but because it was designed to hold 3,000, it can get a little bit crowded. It is, as always, free to the public.
When you're there, check out its Art Deco facilities, decorative glass block, deco-style steel railings, and Art Moderne style ticket booth!