There are so many great trail options out here for every level of hiker and biker. There's enough trail that you'll feel peacefully alone, even on crowded days. I especially like walking the red trail, which is on the North side of the park. Be sure to drive all the way down (keep going!) on the road on the West border of the park, by the old Menninger campus, for some lovely new trails and access to the Kansas River. Walk back up the hill on that road for a heck of a workout.