Starting at 15 Võ Văn Tần, Xuân Hòa, Hồ Chí Minh, Vietnam, open the Explorial app and enter the 6-digit game code that you received by text and Viator chat message. The riddles navigate you through a city that has reinvented itself more than once without losing a step. Your first stop is Ben Thanh Market, the clock-towered landmark at the centre of District 1 whose covered stalls have supplied the city with everything from fresh produce to silk since the French colonial era. Next, the app guides you to the War Remnants Museum, one of the most sobering and important museums in Southeast Asia, whose collection documents the Vietnam War from a perspective that challenges and informs in equal measure. The route then takes you to the Ho Chi Minh City Opera House, a French colonial jewel completed in 1897 that still hosts performances and stands as a reminder of the city's layered past. Around 2 hours on foot. Carry water — the city is warm and busy, and the walk rewards those who move at a thoughtful pace.