Near Mt. Shasta City in the Shasta Trinity National Forest, the 35 mile CC trail has spectacular views of the Castle Crags and forested valleys and peaks. The route follows FS 26 until it forks and takes the unmaintained road to the right to Willits Ravine. Then the loop heads up FS 25 and follows it down to the gravel road which leads back to 1-5 in Castella. Can also loop back around to FS 26 and do a short loop that takes you back to Gumboot Lake.
To reach the mountain biking trailhead from US 5, take the central Mt. Shasta City exit and make an immediate left on W Lake Blvd. Follow to Old Stage Road and turn left. At the Y, stay right and follow signs to Siskiyou Lake. Stay on W.A. Barr Road (FS 26) for 12 miles to Gumboot Lake.
Overall, Castle Crags is the 50th most popular mountain bike trail of all 132 mountain biking rides in California.