With about 30 miles of mountain bike trails, Horsetooth Mountain Park offers almost everything you'd want from a trail network that long. This includes long, hard climbs, flowy sections, fast descents, switchbacks, drops, etc. There's even the occasional fire road to get you from one section of singletrack to the next. The trail surface also varies depending on where you are, with fire roads, packed dirt singletrack, loose dirt singletrack, and rocky sections being some of your options.
One of the easiest ways to access this trail system is through W Country Rd 38E, which wraps around Horsetooth Reservoir to the south and then heads northwest if you're coming from Fort Collins. Follow this road to the Horsetooth Mountain Open Space and turn north a short distance past Overhill Dr to access the parking area.
However, this is not the only trailhead you can use, with plenty of other parking spaces and trailheads in the trail network. Some of the trails in the network include Herrington, Mill Creek, Nomad, Spring Creek, the Stout Trail, Wathen Trail, West Ridge, etc.
Naturally, there are varying difficulty levels. The Spring Creek Trail, for instance, is a diamond black difficulty rated trail and, as such, is only for experts. Some things to expect on this trail if it's on your loop are fairly narrow sections and large rock steps that may be difficult for even intermediate-level riders to navigate. Mill Creek is similarly difficult.
Most of the trails in this park are for intermediate-level riders, with a few easy-difficulty sections as well.
The trail surface will vary, and you can go from a packed dirt section to loose dirt with rocks fairly quickly. There are also plenty of ups and downs, although you can curate your route to have more descents than climbs if that's what it takes to excite you.
Drops are fairly common and will be distributed around the park, and you'll have to deal with sustained climbs in some sections. In fact, you'll have to go through more than 1000 ft of elevation changes in less than three miles in one of the trails.
There are different types of climbs, with some being technical while others require little apart from you pedaling consistently. Naturally, these climbs often lead to exciting payoffs. However, you may not want to reduce your speed on the way down or at least keep your fingers on the brakes since these trails are bi-directional and open to other trail users.
Another common feature is the rock rollovers and tight corners that almost sneak up on you.
Also, after going through a rocky section, you might find yourself on a fast and flowy trail. Alternatively, you may end up in a well-shaded tree section with plenty of roots in the way, so you never know what to expect. This keeps the rides fun, especially if you're new to the trail system.
There is a lack of shade in some sections, so bring plenty of water.
One of the sights you may want to visit while exploring this trail system is the Horsetooth Falls.