Introduction to Yanjiu River: Among the six waterfalls, five lakes and twelve streams, the most famous one is Jiuxi River. One of its streams runs through the three lakes, and is 9 kilometers long from Lover Valley to Ma Daoyakouqing. Because the stream has long eroded the sandstone riverbed containing a large number of nodules, it has formed caves like mortars, which are distributed in a series, hence its name.