Today it is home to New York City's Department of Parks and Recreation and the Central Park Zoo, but the Arsenal, one of only two buildings that pre-date the park itself, was originally built as a military supply depot for New York State's National Guard. It has served many purposes, incorporating at various points a weather bureau, a zoo (with animals from the likes of P.T. Barnum) and a police precinct. From the outside it looks like a fortress, while inside there are rotating art and photography exhibitions, as well as the original, historic "Greensward Plan" detailing Central Park.