Oval Park Recreation Center - click to enlarge

Oval Park, Norwood, Bronx, New York City, winter 2012. Its formal name is Williamsbridge Oval Playground. Originally the site of Gun Hill Williamsbridge Reservoir, constructed in 1884-89, that supplied drinking water until 1919 and then served as a swimming hole until it was drained in 1925. It was converted into a park and playground in 1934-37 in a 1.5 millon-dollar New Deal Works Progress Administration (WPA) project, opening on September 11, 1937, with renovations since then, most recently in 2010-2013. It includes playgrounds for children,

Google aerial view - click to enlarge

a field for football and soccer games, basketball courts, tennis courts, a 400-meter running track, wading pools and sprinklers, dog runs, picnic areas, benches; trees, grass, flowers, and foliage; elevated promenades around the perimeter, and a recreation center with a gym, game room, computer room, and public restrooms. It is also the site of school outings, cultural events, concerts, dance festivals, picnics, celebrations, and just hanging out; it is perhaps the most heavily (and well) used public space in the Bronx. The fenced off area at lower left in the top photo was part of a renovation project completed in November 2013. In the background: Montefiore Medical Center buildings. See lots more pictures of Oval Park in this same gallery you are looking at (the park is more beautiful in the Spring, Summer, and Fall, but then you can't get a panoramic view because of the foliage; see image at bottom).

References:

• Abandoned Land in the Bronx and Upper Manhattan Is Offered by Davidson, New York Times, April 4, 1934: “Two city reservoirs unused for fifteen years, one in Manhattan and the other in the Bronx, have been offered to Park Comissioner Robert Moses to be used as park sites, Maurice P. Davidson, Commissioner of Water Supply, Gas and Electricity, announced yesterday. ... The 13.1 acres of the Williamsbridge Reservoir, just south of Van Cortlandt Park in the Bronx, might best be drained and used for park and playground purposes, in Mr. Davidson's opion. The reservoir is forty-one feet deep.” This Times article is cited by Wikipedia as the source for its claim that the reservoir was originally a natural lake but the Times article says no more about Williamsbridge Reservoir than what is quoted here.
• New 20-Acre Playground Opened in Bronx, New York Times, September 12, 1937: This article affirms the creation of Oval Park by the WPA: ”...the Park Department obtained control of the site on June 27, 1934. Since then ... about $1,500,00 [sic] has been spendt [sic] in buildng up the new facilities. The job was done as a WPA project.” The opening ceremony was presided over by Park Commissioner Robert Moses, Bronx Borough President James J. Lyons, and Captain Howard L Peckham, deputy Works Progress (WPA) administrator.
• NYC Department of Parks Press Release, September 10, 1937.
• Williamsbridge Playground news release, NYC Department of Parks, February 12, 1938.
• Recreation in Parks, NYC Department of Parks & Recreation.
• The Living New Deal, University of California at Berkeley.
• Soll, David, Empire of Water, An environmental and Political History of the New York City Water Supply, Cornell University Press (2013), pp.77-78.