Fantasy Island is a popular area for mountain bikers. It is located on the east side of Tucson near Irvington and Harrison
Directions: Go south on Harrison until it ends and hits Irvington. Drive right across Irvington and park in the dirt lot. Chances are that there will be several parked cars in this area.
I have found Fantasy Island trails to be fun but I have yet to find a good map of the area and the trail intersections are sporadically and poorly marked. If you are not with a knowing local, be prepared to be mostly lost here. You will eventually find your way back to a road but you may ride longer than anticipated. Beginners should ride the Bunny Loop from the Valencia Road parking area. Keep eyes peeled for small trail signs unless you are up for riding the washes at the north end of the area.