George Poston Park has the best dog park within a 30-mile radius.
There is a dog park 5-minute drive away from my home but so few dogs go there that my dog has started to think it's his place now. George Poston Park is at least 20- minute drive from me but I try to take my dog there at least once a week. The area for 25+ lbs dog is huge, mostly covered with grass and pine needles, just how I (and the pup) like it. We always meet plenty of friendly dogs and dog owners there, except for one early Sunday morning when we had the park all to ourselves.
Besides the dog park, there are very nice hiking/biking trails in the park, totaling 6-8 miles. The trails run through woods on small hills, excellent for mountain biking as well as exploration with your four-legged friends.