Sourland Mountain Preserve is a great place for a lot of activities. Personally, we hike here once a year, usually in the fall. The trails are challenging for sure. Steep-ish hills, lots of rocks to step around, and simply great views. The mountain biking here is great. Many groups do group rides here to help show people around. Keep an eye out on the JORBA site for these rides.
We recommend that everyone visit this park. Wear your good biking books, or get on top a full suspension mount bike, and have a great day exploring!