The foothills behind Hughes Stadium has several trail options, all single track. The trail is hard packed and has some rocky sections. One some what difficult climb. And a real downhill section that is optional.
Best route is to ride North from the trail head kirting the side of the hills, but there are also trails south of the trail head. Goinf north the trail will gradually start to climb right behind a fenced in area. Climb up until you are at the road next to the Horsetooth reservoir. You can cross the road and ride the trails that run north and next to the reservoir, which lead to other trails. Ride back the way you came, which is what most people do. Or ride south a 1/4 mile and turn left onto a trail that goes up a steep hill. This trail runs down directly next to the 'A' and is a real downhill trail. No weekend warriors! Middle way down, there are several options to take.
How to get there:
The trails are directly behind Hughes Stadium in Fort Collins. Just south of the intersection of Overland Trail and Prospect Road. Right under the big white 'A'. The trail head on the road just south of Hughes Stadium, right before it starts to climb.