It's common knowledge that spending a couple of hours surrounded by greenery can enhance your energy levels. If wandering around town has worn you out, Genjiyama Park is a perfect place to stop and recharge your batteries.
You're spoiled for sightseeing choice when staying in Kamakura. Genjiyama Park is a great place to start here, but there are many other fine sights to enjoy. Hakkeijima Sea Paradise, Enoshima Aquarium, and Zushi Beach are close to the recreation and green space and and will cap off your day nicely.