The Trail Above Jack Spring Follows The Access Road Used To Maintain Flagstaff City Water Supply Facilities. The Inner Basin Trail Ascends From Lockett Meadow Into The Caldera Of The San Francisco Peaks, An Extinct Volcano And Home Of The Tallest Peaks In Arizona. The First 1.7 Miles Of The Trail Winds Through The Extensive Aspen Forest Flanking The Upper Reaches Of The Peaks, Joining The Waterline Trail Briefly Before Following A Jeep Road Into The Caldera. The Trail Starts At An Elevation Of 8665 Feet, Gaining Approximately 1200 Feet Over 2 Miles On Its Way Into The Inner Basin. The Trail Continues Another 2 Miles, Gaining An Additional 600 Feet Or So To Join Up With The Weatherford Trail. Photo By Deborah Lee Soltesz, August 2015. Credit: U.S. Forest Service, Coconino National Forest. For More Information About This Trail, See The Inner Basin No. 29 Trail Description On The Coconino National Forest Website. Photo