Condon Park is a peaceful place to take a breather. Have a picnic, toss a Frisbee around or just lie on the grass and shut your eyes for a while.
You'll be spoiled for sightseeing choice when staying in Grass Valley. Condon Park is a great place to begin here, but there are numerous other fine sights to explore. Nevada County Fairgrounds, Empire Mine State Historic Park, and Tahoe National Forest Headquarters are close to the recreation and green space and and will cap off your day nicely.