For seasoned skiers looking for a fresh challenge, a gruelling 80km mountain troops circuit through the Italian Dolomites offers the next stage in endurance. Twice as long as the world-famous Sella Ronda circuit and, according to locals, just as beautiful, half the battle of the so-called First World War ski tour is just getting to the start. But having to take two buses with long waits if you miss them keeps away the crowds that plague the popular circuits, says guide Walter Frenademetz. A veteran ski instructor in his seventies, his face is browned and weathered by decades spent on the slope…