Three sections of the upper Arkansas—Pine Creek Canyon, The Numbers, and The Narrows—above Buena Vista are the most difficult stretches of the river commonly rafted by professional outfitters. Until recently, skilled kayakers ran these technical and demanding sections much more frequently than did rafters. Even today, the three sections can only be rafted at certain water levels and outfitters require rafters to be at least eighteen years old, in excellent physical condition, and have had previous Class IV whitewater experience.
     Pine Creek, the uppermost of the sections, follows a very narrow course between an old stage coach road and the railroad. Because of its Class V rapids of the same name, Pine Creek, is considered more difficult than either Numbers or Narrows.
     The Numbers—one to six—is extremely rocky and steep technical Class III-IV+ run that requires coordinated paddling by all participants in order to navigate through and around powerful hydraulics and boulder-filled drops. Paddlers are often too busy to notice the spectacular views of the 14,000-foot Collegiate Peaks.
     The Narrows run, which begins immediately below the Numbers run and ends just above Buena Vista, in early years was often referred to as the Frog Rock and Milk runs. Today, The Narrows can be run by itself, as a continuation of the lower part of the Numbers trip, or as the first day of a two-day Narrow/Browns Canyon trip. Narrows features continuous Class III-IV with pourovers, hydraulics, and standing and breaking waves. Frog Rock Rapid, a long rapid filled with boulders, holes, and waves and House Rock Rapids are the Narrows most notable rapid.  The later received its name from a house-size boulder located midstream that parts the waters between two already very narrow walls. It is commonly said that only the guide knows whether to go right or left.