Southeast of Green River in Goblin Vallley State Park, the Wild Horse Mountain Biking Trail System consists of five loops through red rock valleys. The outermost loop route is roughly 6 miles, while the inner loops are about 1.25 miles each.
To reach the Goblin Vallley State Park trailhead from US70, use Exit #147. Head south on SR24 for 23.5 miles. Turn right heading west on Temple Mountain Road for 5 miles. Turn left heading south on Goblin Valley Road for 7.4 miles into Goblin Vallley State Park (stay to the left to find the main hiking area amongst the goblin rock formations).
Since Goblin Vallley State Park is quite crowded on the weekends, make sure to try a weekday or arrive very early.
Overall, Wild Horse Mountain Biking Trail System is the 72nd most popular mountain bike trail of all 74 mountain biking rides in Utah.