This is a good trail system to ride when the foothills and mountains are covered in snow. Located just to the south of Green Mountain, it provides a close-in alternative for riders to get some exercise in the winter months. I rode it in late December and was practically the only person in the entire park. The trails are generally singletrack, although a few are shared with horses (with associated issues). There is one minor hill climb but many ups and downs throughout the park. There are a variety of trail options and directions, but given the size of the park, it is impossible to get lost here. Ridden at high speeds and high energy, you can still get a good workout on this system. Most of the trails are well kept and the ones I hit were very low on the technical scale. Probably similar to the trail that goes around the western base of Green Mountain. Nonetheless, it made for a nice change. I believe the park also hosts a MTB race - which is what got me curious enough to check it out.
The easiest way to get there with a bike is to park at the Morrison Exit of C-470 (there is a small lot on the NW corner of Morrison Rd. and C-470). From here you can connect to the bike path that goes under C-470 and immediately you enter Bear Creek Lake park. Otherwise, you can park inside the park, but there is a fee to do so.
http://www.singletracks.com/item.php?c=1&i=1109