Cambodia's Angkor complex spreads 400 sq km of temple ruins around Siem Reap with Angkor Wat, Bayon's faces, and Ta Prohm's tree-strangled walls, plus the Killing Fields of Choeung Ek outside Phnom Penh.
Cool dry season with Angkor sunrise at Wat at peak photographic conditions, Phnom Penh walking comfortable, and Water Festival in early November.
Hot dry season hits 38°C and Angkor walking punishing by 10am, but Khmer New Year mid-April fills temples with offerings and brings water-fight street celebrations.
Wet season with afternoon storms, Tonle Sap lake at peak level expanding floating villages, and Angkor temples photogenic in the green monsoon light.
Pchum Ben fortnight in late September-October brings family ancestor offerings to pagodas across the country, the country's most observed religious period.