Starting at Av. dos Descobrimentos B, 8600-722 Lagos, Portugal, open the Explorial app and enter the 6-digit game code that you received by text and Viator chat message. The avenue takes its name from the discoveries that set sail from this very coast. The first clue leads to the Muralhas de Lagos, the medieval city walls that once enclosed a town at the forefront of European maritime ambition, and whose towers and walkways offer views over the old city and the Rio Bensafrim below. From there the app takes you to the Antiga Câmara Municipal, the former town hall whose graceful 18th-century loggia faces the main square — a handsome survivor from the city's rebuilding after the 1755 earthquake. Your final stop is the Mercado Municipal de Lagos, a covered market built in Moorish-revival style, still trading in fresh produce, fish, and local crafts beneath its decorative arches. Around 2 hours on foot through the compact old town. The beach can wait — the history is just as rewarding.