Starting at the Parc du Champ de Mars on Avenue de la République, you'll open the Explorial app, enter the 6-digit game code that you received by text and Viator chat message, and stroll into the old town. The tour is fully self-guided — no guide, no fixed start time, just your group and the city. Place Rapp opens the hunt beneath the statue of Napoleon's General Rapp, a local boy made good — or at least made bronze. Riddles brief you on his exploits. Then La Petite Venise takes over: flower-draped canals, fishermen's cottages and reflections that fill camera rolls. The photo task here is almost unfair. At the Place de l'Ancienne Douane, trivia unpacks the Koïfhus, the old customs house where Alsatian merchants weighed goods and settled scores. Around two hours through a town that inspired fairy-tale illustrators. The leaderboard names the fairest of them all.