Starting at the Centro de Turismo Sol on Puerta del Sol 5, the very centre of Spain's road network, you'll open the Explorial app, enter the 6-digit game code that you received by text and Viator chat message, and dive in. The tour is fully self-guided — no guide, no fixed start time, just your group and the city. In the Plaza Mayor, the riddles pull you around the arcades and frescoed facades of a square that has seen everything from royal weddings to the Inquisition. Nearby, El Oso y el Madroño — the bronze bear reaching into a strawberry tree — poses questions about the symbol Madrileños have claimed since the Middle Ages. The route then winds to the Plaza de Oriente, where rows of stone kings face the Royal Palace, each statue with a story the app is happy to quiz you on. Count on roughly 2 hours, tapas stops optional and encouraged. By the end, the historic centre will feel like a story you helped tell.