North of Boulder and west of Longmont, the Heil Valley Ranch has a 9+ mile trail system open to mountain biking.
To reach the Heil Valley Ranch mountain biking 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 Heil Valley Ranch 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 ride, turn left on the Ponderosa Loop riding it clockwise. About 1 mile through the loop near the overlook, veer left onto the newer Wild Turkey Trail. This fast rolling trail runs about 2.9 miles back to the Ponderosa Loop near the intersection with the Wapiti Trail. Then is a wild, rocky downhill back to the trailhead.
Overall, Heil Valley Ranch is the 21st most popular mountain bike trail of all 176 mountain biking in Colorado.