If you are visiting Chico and have a need for a little or a lot of exercise Bidwell is great. The terrain is both flat and at the north end hilly. The park follows a creek part of the way and has great bird-watching all along. The nature center parking lot is wonderful birding without even going for a walk.
Bidwell Park and the bike passages in Chico should keep bikers happy for days. And then of course there is the Sierra Nevada Brewery for the end of the day.