Starting at the Rotonde du Mont-Blanc on the lakefront, you'll open the Explorial app, enter the 6-digit game code that you received by text and Viator chat message, and follow the water toward the old town. The tour is fully self-guided — no guide, no fixed start time, just your group and the city. The Île Rousseau floats first into view, its statue of the philosopher gazing over the Rhône. Riddles ask what Geneva's most famous son actually thought of Geneva. Up in the old town, the Cathédrale Saint-Pierre holds Calvin's plain wooden chair and 157 tower steps with a view worth every one. Trivia handles the Reformation politics. Then the Mur des Réformateurs stretches its hundred metres of stern stone faces across the Parc des Bastions — post tenebras lux. Around two hours between lake and history. The final leaderboard is strictly neutral — the winning, less so.