Updated description by mtbgreg1, circa 2010:
Detailing one specific route at Big Creek is impossible. I will cover the area in detail below and attempt to include directional information as I do so, but it will be up to you to choose the best route after that. Don't worry, the trail signage is very thorough and will be sufficient to keep you from getting too turned around.
Cross Country Mountain Biking
The 6 or so miles of cross-country oriented singletrack trails of Big Creek are well-maintained, well-marked, and entertaining to ride. The trails are labeled with different colors based on their level of technical difficulty, so its easy to pick the trail that will serve your needs the best.
The black/advanced trails feature plenty of rocks, some log rides and other features, a few stiff climbs, and a couple of drop offs.
Most of the trails are directional, so check the signs and pay attention to what day of the week it is!
While the cross-country trails are pretty cool, Big Creek's true claim to Atlanta area fame are its downhill and dirt jump-oriented trails. From what I hear, there is really no other place in Atlanta with this kind of riding, and possibly only 1 other place in the state of Georgia with downhill-specific trails! There are about 5-7 different trails to choose from packed tightly together on a hill side located about a mile down the greenway. There are also a number of rock drops spread throughout the area, with 4 or so on the backside of the upper ridge dropping down towards a maintained park.
I've ridden my All Mountain bike down many of these trails before, and I've heard people say that they really don't live up to true downhill-oriented trails. While that may be true, I know that I definitely don't feel comfortable on a 5" travel bike bike when:
pinning it (that means going completely balls-out high-speed for those not familiar with moto lingo) through the rock gardens containing mini boulders and 3 foot drops after many of the rocks
sending a 3 foot high booter to a super long landing (where you could get as much air as you want)
airing a 15 ft long table top
doing various rock drops ranging from 4ish feet to 7-8 feet
Bearing in mind that these trails are located in Atlanta, I'd say the terrain is pretty freaking sweet!
Big Creek has a dedicated line of high-quality purpose-built dirt jumps that run along the top of the ridge above the other downhill and freeride runs. There are a mix of different size jumps ranging from relatively small to one with a lip that's pushing 6 feet high or more. To the best of my knowledge, there is nowhere else in Atlanta, or even the state of Georgia for that matter, with an area that even comes close to comparing to the near-professional grade of these jumps. While most of the riders I have seen sessiong them have been on dirt-jumping mountain bike frames, I've witnessed a number of BMXers sending it big time as well.
Located directly in the center of all of the action, the banked slalom-type course seems to be the focal point of all the attention. It is appropriate that all the other trails seem to be built around it, as riders of all different disciplines can navigate the slalom run. For instance, when I was last out at Big Creek, I saw a kid on a rigid single speed 29er rolling down through the berms.
So granted, the big berms and flow are going to be accessible to anyone on almost any bike. To really rail this trail and air out the big table tops, however, you're going to need to be riding something much more aggressive than a rigid SS 29er. A dirt jump bike would be perfect for this kind of work, and a BMX bike or a downhill bike would also function passably, despite being on opposite ends of the bicycle-size spectrum.
One of the newest additions to Big Creek is a pumptrack with beginner and advanced lines. Come here to get your first taste of rollers and berms, or to rack the speed up and get your flow on!
Night riding at specific times, with approved leaders only.