The Forest Ecology Preserve is a nature park located out on College Street past the fisheries. Admission to the preserve is free to the public and it is open 7 days a week during sunlight hours. There are hiking trails, a pond, a turtle habitat, a bird viewing area w/ scope, a butterfly garden, nature playground and lots of other cool things to explore there. They are also always putting on various events that are usually interesting and cheap.
They recently started a Facebook page where they are able to post a myriad of updates. There are updates on there from upcoming events to hey the irises are blooming at the pond right now. I would definitely recommend checking it out.