Forest Park is the largest urban park in the United States. There are a few that are bigger within a city's official border (Phoenix, Boise) but they are in unpopulated areas. Ours is significantly bigger than Central in New York or Golden Gate in San Francisco, which would probably be most people's guess, and smack in the middle of town. The city is hard up for money but the park has been maintained and greatly improved by a private foundation, Forest Park Forever.
I have 513 photos of the park on Flickr (and I have not been good about keeping it up to date lately). No way to pick just one. Two was difficult. The first picture is the top of Art Hill in October with the iconic statue of Louis IX of France. The second is the balloon glow held the night before the Great Forest Park Balloon Race, which may or may not take place September. If I am at a loss for something to shoot, there is always material there.