Big Haynes Creek Nature Center (Georgia International Horse Park) - Bike only trail is a 5.1 mile moderately trafficked loop trail located near Conyers, GA that features a river. The trail is good for all skill levels offers a number of activity options. Dogs are also able to use this trail but must be kept on leash.
dogs on leash
I have ridden the bike trails here and are awesome. The half near the hiking trail is tough. You think you are pretty good and it will humble you.
There are over 20 miles of trails. All are well marked. You can find a map at http://www.georgiahorsepark.com/Portals/4/GIHP%20trails%20map.pdf
All of the trails are marked. The horse trails are better to walk on then the bike trail. The nature center has abou 3 miles of trails with no bikes or horses. You can also canoe or kayak there.
I have hiked this trail and I like it because it is close to my home and it is easy access, for a hiker, you are taking your life in your hands because bikers are not going to look for you (it is a mountain biking trail). It is not an easy trail, it is a mountain trail after all, but I would say the average person can hike it with a medium amount of effort. I think that next time I will try hiking it backwards so I can see the bikes coming. There are also a number of horse trails that can be hiked at the park that might be safer, but I'm not sure how well they are marked.