Sion is a city in the southwestern Swiss canton of Valais. It’s known for 2 hilltop fortifications: the 13th-century Tourbillon Castle ruins and the Valère Castle complex, with a basilica housing an organ over 500 years old. The 15th-century Cathedral of Notre-Dame-du-Glarier and the conical Witches’ Tower are in the old town. The Majorie and Vidomnat towers house the Valais Art Museum’s regional art collection.