Note: These trails are primarily mountain bike trails, so expect significant mountain bike traffic.
That said, this is a beautiful trail with a couple of cool views and some nice rocky, exposed singletrack.
From the I-75, take I-575 north. Exit at Towne Lake Parkway and turn right. Make your first left onto Woodstock Parkway and follow it until it dead ends into Olde Rope Mill Rd. Make a left. Make your first right onto Rope Mill Rd. The park will be at the end of the road.
http://www.tripleblaze.com/trail.php?c=3&i=1463