The trails here are some of the best, truely intown riding, that Atlanta has to offer. Be prepared to get muddy though; almost all the times that i have been here i have ended up extremely muddy. There is great single track for all levals of riding, including some pretty hairy down hills and a section of great whoop-to-dos. If u r the rider who loves the technical side of mountain biking and the great single track, then the waterworks is for u.
"From I-85 south, exit left on to North Druid Hills Rd. Proceed to Clairmont Rd and make a right. Then make a left onto Mason Mill Rd. From there go to the bottom of the hill untill u see an old, muddy road that leads to some rail road tracks. Cross the tracks and and down a little path goes past some ruins of an old mill (there r trails that go past the mill but they r growm over) and then cross a bridg. The trails proceed in either direction with lots of other trails that branch off of them.
http://www.singletracks.com/item.php?c=1&i=601