Maps are available. Otter Creek is probably the best trail in the surrounding area. From rock climbs to very fast downhills, it will test your ability. It may not have the recognition it deserves, but hopefully someone will realize what is hidden at Otter Creek. Several trails in the Park, but Blue Trail is the longest route with the most variety.
Yellow trail offers some tough climbs or fast downhills.
Waverly Park and Fort Duffield are good trails in the area as well. Submission above it says the trail is 10 miles, but I thought it was more like 14 or 15. Most of the technical sections can be easily walked or bypassed for beginners. Otter Creek is a good park at which to take a picnic lunch and spend the day. The trail is rideable by most levels of riders, but you can expect to spend some time there.