Starting at Tom Watson Park, this route is 20 Mile loop.
This 20 mile loop is perfect for a long run during the winter months. With some moderately challenging hills, the route is run mostly on dirt roads, light trails, and roads. With a view of the Flatirons in the distance you’ll be sure to find motivation with each step. Starting at Tom Watson Park, just to the east of the Boulder Reservoir, the first two miles of the route run through Boulder Reservoir Park. You’ll exit the park at 51st Street, and head north along the dirt road with the mountains to your left.
Just after three miles, you’ll reach the top of the hill and the entrance to Eagle Trailhead, where you’ll turn left and run the well-groomed trails of Boulder Valley Ranch. The 5 mile marker is at the corner of Sage Trail and Left Hand Trail, where you’ll head north and roll for a few miles. You’ll reach the 6 mile marker just at the tip of Left Hand Valley Reservoir. You’ll exit the trails at Neva Road, and continue heading north on 39th. By now you’re quads may be burning, as you’ve been climbing for the majority of the run, but don’t worry, the run reaches its’ peak just after 11 miles, at the corner of 39th and Nelson Road, where you’ll run by Altoona Grange.
From here, the run begins a very gradual descent along Nelson road, as you head east towards Longmont. You’ll run along Nelson for nearly 2 miles before turning south on 55th, and return back to the dirt roads. Save a little something from this section, because there’s a few rolling hills along 55th. When the road comes to a dead end at Oxford, you’ll head back east and climb a moderate hill until rolling back down to 63rd, where you’ll head south. From here, it’s all road, and a straight shot back to Tom Watson Park.
To watch a fly-over of the course, download the Google Earth plugin if prompted.