The region consists of the area around Meiringen and Hasliberg up to Grimsel Pass ( ) , around Lake Thun ( ) and Lake Brienz , and the valleys of many high mountains with the towering Jungfrau Peak ( ) , the area southwest of the Lake Thun with Kandersteg ( connection to the Valais ) and Adelboden , and the area round Gstaad and Lenk in the Simmental .