North of Boulder, the Heil Valley Ranch has a 10+ mile trail system open to hiking.
To reach the trailhead from Boulder, head north on SR36. In Altona, turn left heading west on Lefthand Canyon Drive for about 0.6 miles. Turn right heading north on Geer Canyon Drive for about 1.2 miles. The trailhead is on the right. The total mileage is 9.5 miles.
From the trailhead, the main Wapiti Trail climbs consistently for 2.5 miles through ponderosa pine forest to the intersection with the Ponderosa Loop. The trail is a packed, rocky surface. For the best hike, turn left on the Ponderosa Loop hiking it clockwise. About 1 mile through the loop near the overlook, veer left onto the newer Wild Turkey Trail. This rolling trail runs about 2.9 miles back to the Ponderosa Loop near the intersection with the Wapiti Trail. Then is a rocky downhill back to the trailhead.
Note: This trail system is very crowded on the weekends, especially from 10am to 4pm. It is very popular with mountain bikers. Consider exploring this trail system early on weekdays.
Overall, Heil Valley Ranch is the 55th most popular hiking trail of all 72 hikes in Colorado.