Starting at Cais das Portas do Mar, R. da Porta Nova, 8000-250 Faro, open the Explorial app and enter the 6-digit game code that you received by text and Viator chat message to begin. The route begins at the old sea gateway and leads directly into the Cidade Velha — Faro's walled Old Town, one of the best-preserved in the Algarve. The first riddles take you to the Igreja de Santa Maria, the city's main cathedral, built on the site of a Moorish mosque and still standing watch over the ancient walls. Next, the trail leads you to the Arco da Vila, Faro's elegant neoclassical arch — built in the 19th century on the site of an old Moorish gate — and one of the city's most photographed spots. The app then guides you to the Palácio Belmarço, a striking 17th-century manor that has survived centuries of change and still dominates its corner of the Old Town. Around 2 hours of walking, any group size. A fully charged smartphone with mobile data is required.