This trail is made up of two distinct portions, the climb and the downhill.
Begin this ride with a doubletrack climb from the Pauley Creek intersection to the top of the ridge where Big Boulder trail starts. Some sections are pretty steep, some are loose, some are both. It's a bit of a grinder, but you'll be rewarded in spades.
Once you get to the top of the ridge, continue onto the Big Boulder Trail. You'll begin a well-earned descent here, and one that is as much fun as you can find anywhere in the Downieville area (in my limited experience, mind you). This downhill is my favorite section of anything I've ridden there. The trail is fast, flowy, a little technical, and a little dangerous. You'll head through exposed sections and through the woods, FAST.
This trail dumps you on Third Divide for more fun and fast downhill.