The Adam's Gulch Trail is ride 26D in the, "Mountain Biking Sun Valley, Idaho" guidebook but there isn't much of description. The trail starts out as a nice climb up Adam's Gulch via the Shadyside trail and continues to be a nice ride until you hit the last three miles of the ascent. The trail turns into hike-a-bike for the mile or so and the mile before that is more dismountin' biking than mountain biking. Don't let this part of the trail discourage you. As you approach the top, you get some killer views down into Adam's and the Pioneer mountains. You'll know you're at the top of the difficult climbing when you arrive at the pond and burned area - a surreal area worth taking a break for carbs and photos. The descent is a fun mix of technical (nothing too over the top), singletrack and short climbs. The descent is worth all the pushing and getting off and on the bike. If you're reasonably well conditioned, you'll probably be tired but not too exhausted after the ride. Intermediate riders should approach the descent with some caution since the rocky sections tend to sneak up on you and the trail is pretty narrow from what I assume is little use - we were the only tracks visible on the trail and it hadn't rained in days.