Guide to four hut-to-hut treks in the Austrian Tirol: the 9-day Zillertal Rucksack Route/Berliner Hohenweg, the Zillertal South Tirol Tour and the Peter Habeler Tour (both 7 days) and the Olperer Runde Tour (6 days). With optional excursions to climb neighbouring peaks, some of which call for mountaineering skills and glacier crossings.