Pellier Historical Park is a lovely place to take a break. Enjoy a picnic lunch, amble around the grounds or just lie on the grass and close your eyes for a while.
You'll have sightseeing choices galore when in Downtown San Jose. Pellier Historical Park is a great place to start here, but there are plenty of other worthy sights to enjoy. California's Great America, Santa Clara University, and Winchester Mystery House are close to the recreation and green space and will fill in your day nicely.