Panorama Trail Loop in Yosemite National Park. ~14mi, trailhead-to-trailhead (+ ~3 miles road walking between trailheads = nearly ~17 mi total) Depending on the season / trail conditions, can use the JMT section or Mist Trail section to/from Happy Isles Trail Head. Can do counterclockwise (typical) or clockwise. Can be a day-hike or backpacking trip. For a backpacking trip, permit is required, with specifications on where you can camp.