Forestville Mystery Cave Trail is a standout hiking destination in Preston, MN, covering 4.0 miles with 300ft of elevation change. Stats: 4.0 miles, 300ft gain, Easy. Type: Loop. Surface: Dirt. Time: 2 hours. Fee: $7/vehicle. Dogs: Yes, on leash. Permit: No. Wildlife: deer, turkeys, bats. Best seasons: Cave tour and bluffland forest. Pack water, layers, and appropriate footwear. Conditions vary across MN. Leave No Trace: stay on trail, pack out all waste, respect wildlife.