Thun stacks a 12th-century castle above a medieval market street with raised sidewalks — and drops the whole arrangement beside a turquoise Alpine lake with the Eiger on the horizon. This app-led scavenger hunt takes you through Thun on foot, using phone-based riddles to guide you from one landmark to the next. No guide, no fixed start time. • Cross the Rathausplatz, the arcaded square at the foot of the castle hill • Climb to Schloss...