Departing Brown Mountain Overlook, hikers drop 400 feet in about .75 mile from the Skyline Drive into the gap that separates Rocky Mountain from the main ridge occupied by the scenic road. In the gap, the blue-blazed Rocky Mountain Run Trail leads left, and is the return route for both hikes. The trail gradually descends past Brown Mountain and down to the Big Run Portal Trail in about 4.5 miles, approximately 5.5 miles from the Skyline Drive . The shorter hike heads left up the yellow-blazed Big Run Portal Trail, but downstream, and across a bridge, the trail passes through The Portal. Going upstream, Big Run rushes along the trail, actually a fire road.
Big pools tempt hikers in the heat of summer.
After four stream crossings, which can be difficult in high water, the Rocky Mountain Run Trail goes left. That junction is about a mile from the Brown Mountain Trail, and about 6.3 miles from the Skyline Drive. In about three miles, the Rocky Mountain Run Trail regains the ridge of Rocky Mountain after a strenuous climb. Hikers turn right, to the Skyline Drive's Brown Mountain Overlook, and a total mileage of just under ten miles. The trail climbs out of The Portal area with switchbacks, crosses talus slopes, and offers distant views on its way to the blue-blazed Lewis Peak Trail, about 3.5 miles from Big Run Portal Trail and just over nine miles from the Skyline Drive.