Ashton Wildwood Park is only about 30 minutes NE of Des Moines and houses the Des Moines Astronomical Society’s observatory. There are also wooded hiking trails and softball facilities.
Neal Smith Wildlife Refuge has miles of beautiful prairie, a cool indoor learning center, paved trails, and a bison/elk herd.
Badger Creek State Recreation Area is a popular fishing destination, with a large lake. There are no designated trails but there is wooded space to explore as well. Every year in mid-July, there is a large sunflower field that is popular for taking pictures (details below for the 2017 field location).
Lions Park is in Windsor Heights.
Sunset Park has soccer fields and open green space.