Starting at Rua Dr. Alfredo da Costa 5, you'll open the Explorial app, enter the 6-digit game code that you received by text and Viator chat message, and follow the lanes into Sintra's wooded hills. The tour is fully self-guided — no guide, no fixed start time, just your group and the city. The route leads past the Palácio de Seteais, the 18th-century palace-hotel whose arch frames the Moorish castle above. Riddles unpack the 'seven sighs' of its name. At the Chafariz Manuelino, trivia flows with the spring water that supplied Sintra for centuries, carved in classic Manueline flourish. Then the Quinta da Regaleira takes the stage — gothic pinnacles, symbol-laden gardens and the famous initiation well that riddles can't resist. Count on around two hours in Sintra's microclimate, so pack a light layer. The leaderboard settles who solved the mountain's mysteries.