Vietnam's outdoor landscape runs for 3,400 kilometres of north-south range with complete climate transitions. The northern highlands around Sapa — where terraced rice fields rise through mist on the flanks of Fansipan (3,143 metres, the highest peak in Indochina) — offer multi-day trekking through minority ethnic village landscapes of rare visual and cultural complexity. Ha Long Bay's karst tower islands are sea-kayakable from inside — paddling into sea caves, floating beaches in enclosed lagoons, and cliff-face passages accessible only at low water. The Phong Nha caves system in Quảng Bình province holds the world's largest known cave passage (Son Doong, with a jungle and river system inside a single chamber 9 kilometres long) alongside kayakable rivers and jungle hiking. The Mekong Delta south of Ho Chi Minh City is a boat landscape of extraordinary biodiversity. The best part is often the hidden gems you were not even looking for. Take it all in.