Lake Hongze is the fourth largest freshwaterlake in China. Lake Hongze has quadrupled in size since the 12th century. A particularly large change happened in 1680 (the 19th year of the Kangxi era), when the Yellow River changed its course and merged with the Huai River. Heavy sediment from the Yellow River blocked the course of the Huai River and diverted water from the Huai, creating Hongze Lake as we know it today. The city of Sizhou was completely submerged, as was the nearby early-MingMing Ancestors Mausoleum. The latter was rediscovered only in the 1960s.