Heckscher Playground building, which also serves as the main entrance to the playground. "The present recreation building, which served primarily as a comfort station, will be remodeled to provide recreation rooms for cold and inclement weather, and a heating plant will be installed so that it can be used throughout the year."[1]

References:

1. NYC Parks Department press release, March 24, 1935, plan for Heckscher Playground renovation.
2. NYC Parks Department press release, December 30, 1936, opening of reconstructed Heckscher Playground.
3. Federal Writers' Project, The WPA Guide to New York City, Random House (1939), p.351: ”Heckscher Playground—a venture in which philanthropy and the Works Progress Administration have combined to provide for the recreational needs of children.”
4. New Deal Assistance in NYC Parks Department Projects, 1934-43, which explains how all Parks Department work 1933-1938 (and much of it until 1943) was with New Deal, funding, labor, and/or design.