There is a network of cross-country trails around the cycling park: Veteran's Trail, Big Springs Loop, Rabbits Run, D's Chaos, Twisted Sister, and Junk Yard. The singletracks is new but sandy and needs to be worn in. Also at the park are: Four Cross Course, Dual Slalom, Gravity Lines, Jump Park, Pump Track, Skate Park, and Velodrome. Great Venue with a variety of riding for all.
Take W. State Street (Idaho HWY 44) west from downtown Boise or east from Eagle to N. Horseshoe Bend Road. Take N. Horseshoe Bend Rd. north for about 2 miles. The park will be on your right. You can't miss it.
http://www.singletracks.com/item.php?c=1&i=2804