The Turtle Pond, a man-made pond, is at the southern edge of the Great Lawn. The pond was originally part of the Croton receiving reservoir.[50][51] The receiving reservoir was drained starting in 1930,[52][53] and the dry reservoir bed was temporarily used as a homeless encampment when filling stopped during the Great Depression.[51][54][55] The Great Lawn was completed in 1937 on the site of the reservoir.[56] Until 1987, it was known as Belvedere Lake, after the castle at its southwestern corner.[50][51]