Haimenkou is one of the most important prehistoric archeological finds in Yunnan: a stone-age settlement near Jianhu Lake in modern day Jianchuan. It is one of the earliest villages excavated in China.  

What was found, over several excavation periods, was the wooden foundations of a lakeside village, with a number of stone age and bronze age tools. 

There is not actually much to see at the actual site, about 1km towards Jianhu from Diannan, on the right side of the highway.