The chance to run whitewater in a canyon twice the depth of the Grand is reason enough to head for the Cotahuasi—and the rapids truly are extraordinary: At its late-spring peak, the froth flows for a hundred miles at continuous Class IV, with some stretches of Class V. Set out from the so-called White City, Arequipa, a former Spanish colonial settlement built mostly of pearly volcanic rock. From there, a 15,500-foot pass leads to the remote village of Cotahuasi, "a happy little place in the middle of nowhere," as BioBio Expeditions river guide Marc Goddard puts it. Then take a ten-mile, mule-assisted hike skirting thundering Sipia Falls before commencing seven rollicking days on the river.
Vitals: The Cotahuasi is at its best in May and June. BioBio Expeditions runs an 11-day trip starting June 6 ($3,300; bbxrafting.com).