Starting at Grabenstrasse 22, at the edge of the old town, you'll open the Explorial app, enter the 6-digit game code that you received by text and Viator chat message, and slip into the alleys. The tour is fully self-guided — no guide, no fixed start time, just your group and the city. At the Obertor, the riddles start where travellers have entered Chur for centuries — a stout medieval gate that once locked the city up at night. The Arcas square is the old town at its best: a sloping plaza framed by painted townhouses and café terraces, with details on every facade worth a closer look. Fontanapark offers a greener puzzle stop, gathered around the monument to Benedikt Fontana, the Graubünden folk hero who fell in battle in 1499 — the app will tell you how, if you answer right. Around 2 hours through 5,000 years of history, breaks included. By the end, Chur will have proven that age is just a number.