Kilauea Iki Trail
Walk across a crater floor that was a lava lake in 1959.
You drop through rainforest, cross the hardened lake past steaming cracks, and climb out the far side. It's a 3.3 mile loop from the overlook, longer from the other trailheads. Overlook parking is tight, so the park suggests starting at the visitor center or Devastation Trailhead instead.