Another classic or classics, take the Inverness train, off at Blair Atholl up Glen Tilt up to the Geldie and either continue up to and through the Lairig Ghru or Glen Geldie/Feshie and up to Aviemore for the return trip. Take 2 1/2 days over it, bothies en route, Corrour in the Lairig or Ruigh Aiteachain in Glen Feshie.