The Liangzhu culture is a Late Neolithic society of the lower Yangtze River in eastern China, flourishing from about 3300 to 2300 BCE around a large walled city near modern Hangzhou. It is best known for its finely carved ritual jades and as a highly stratified, urbanized polity often described as one of the earliest states in East Asia. Its inscription as a UNESCO World Heritage site in 2019 was widely presented as proof that Chinese civilization is five thousand years old.
About five thousand years ago, on the flood-prone plain south of the Yangtze, the people of Liangzhu raised something no earlier society in the region had attempted: a sprawling network of dams, levees, and reservoirs to hold back the water and store it. It was among the oldest large-scale waterworks anywhere on earth, and only a society that could command thousands of laborers for years could have built it. Yet around 2300 BCE that world came to an end, and the leading explanation points back to water. On this reading, an age of violent monsoon floods overwhelmed the defenses, buried the city under river mud, and undid the very people their mastery of water had raised up. The evidence for it is powerful but not conclusive, and social or political strains may well have combined with the flooding.