Context: The Alps have been crossed for war and commerce, and by pilgrims, students and tourists. Crossing routes by road, train or foot are known as passes, and usually consist of depressions in the mountains in which a valley leads from the plains and hilly pre-mountainous zones. In the medieval period hospices were established by religious orders at the summits of many of the main passes. The most important passes are the Col de l'Iseran (the highest), the Brenner Pass, the Mont-Cenis, the Great St. Bernard Pass, the Col de Tende, the Gotthard Pass, the Semmering Pass, and the Stelvio Pass.

Question: What have been crossed for war and commerce? 
Answer: The Alps

Question: What was established during medieval periods by religious orders?
Answer: hospices

Question: Where were hospices established? 
Answer: the summits of many of the main passes

Question: What is the highest of the most important passes of the Alps?
Answer: Col de l'Iseran