Building 502 was constructed as an ordnance shop for the assembly and repair of harbor mines, then called torpedoes, and other artillery. It stood next to the torpedo magazines and a tunnel leading down to the Water Battery, with a railway from the tunnel providing easy access to the water. A wooden elevator transferred torpedo components between the building’s three floors. Since 2008, Building 502 has served under the Urban Park Rangers as the Fort Totten Visitors' Center, where visitors can learn about the park’s military past, the natural history of the parks, and the city’s diverse urban wildlife, and can find out how to visit Fort Totten’s historic Water Battery.