Grimes Farm and Conservation Center just outside of Marshalltown is a great place to hike and play. Hiking trails provide access to forests, wetlands, prairies, and crop fields. My 6 year old boys love the natural playscape, the storywalk and observation tower.
The observation tower is a 0.6 mile hike from the parking lot. Walk toward the nature center and you'll see a sign pointing in the direction you need to walk. The hike is on wide grass paths.
The natural playscape is a large area with many fun elements including a slide, a music area, a butterfly garden, a swing, a spider web, and a sand play area.
The current storywalk book is Over and Under the Pond. It's along the Boardwalk Trail, starting at the playscape and ending at the nature center.
There are several picnic tables near the playscape, some of which are under a shelter.
From the parking lot, look for this bridge which leads to the nature center and the trail to the observation tower. The center is only open on weekdays, however there's a portable restroom in the parking lot.