Fun short ride, no long climbs at all. Fairly bumpy even with full suspension. Theres another trail going west across the road from the loop with some nice views at the end. Often I find myself ready to ride more after this trail because its 5 miles and not very strenuous, if this happens to you, I'd recomend Hall Ranch loop, only about 10 minutes to the west, and listed on this site.
From Boulder, CO. go north on Highway 36 to Lyons, there will be a light here and you can only go left or right, go right(East) on Highway 66 for about 1 mile. Turn left on 53rd street, there should be a sign here for Rabbit Mountain open space. go almost 3 miles and you will see the parking lot on the right.
http://www.singletracks.com/item.php?c=1&i=1189