Starting at Jardin de Ville, 38000 Grenoble, France, open the Explorial app and enter the 6-digit game code that you received by text and Viator chat message. The riddles lead you across Grenoble's historic centre, from riverbank to revolutionary square. Your first stop is the Passerelle Saint-Laurent, a footbridge spanning the Isère with views of the old city and the mountains closing in on all sides — Grenoble's geography laid out in one glance. From there the app takes you to the Fontaine des trois ordres, a fountain commemorating the 1788 Day of Tiles, when Grenoble's citizens threw roof tiles at royal troops in one of the first acts of resistance leading to the French Revolution. The route concludes at Place Victor Hugo, a grand leafy square at the heart of the modern city — part civic gathering ground, part elegant promenade. Around 2 hours on foot. The app works whatever the weather, and Grenoble has no shortage of excellent spots to stop for coffee along the way.