Yansai Lake, also called Shihe reservoir, is located in the canyon 7 li northwest of Shanhai Pass. It is the first man-made lake along the East Great Wall. It was constructed in 1974 when people built dam for reserving water. Shihe was a river which overflowed every summer and fall. The flood running through the narrow winding riverbed damaged the farmland and blocked the villagers. Shihe, however, is a natural protection for Shanhai Pass. A lot of military and national conflicts happened in this place during Sui, Tang, Liao and Jin dynasties. Li zicheng, a farmer uprising hero in the end of Ming dynasty, had a ferocious battery at the banks of shihe with Qing army led by Duoergun. In Beiyang government's reign, two wars took place here. It is the very place that He zhuguo resisted the Japanese invading troops.
After the founding of PRC, the native people spent only 3 years on the dig of this lake, which blocks the flood in the canyon. From then on, the new lake becomes a scenic spot of north China. With the lake area of 15 square kilometers, the lake today is like a beautiful picture, in which boats sailing on the water and different sceneries taking on alternatively. Besides beautiful water, Yansai Lake also processes marvelous stone and unique sceneries, such as the sword-like peak in the island in the center of the lake, etc. The lake was appreciated by poets as a combination of Guilin style beauty and tree gorges-like grandness. It is like a pearl beside the Great Wall, adding great beauty to it.
The original name of Yansai lake is Shihe reservoir. It was built in 1975. With the capacity of 68 million cubic meters and water area of 4.5 square kilometers, the lake is one of the most famous reservoirs of China. In 1979, it was developed for tourism and renamed Yansai lake. A 300-meter long and 60-meter high (highest point) cableway was built in 1985. In 1988, the project “forest of bird”, which covers an area of 15 thousand square meters, opened up for the raising of some precious birds like black swan, red-crowned crane, etc. The dam of the reservoir is 365 meters in length and 44.6 meters in height. An overview of the lake can be seen from the peak.
Narrowness and winding are the characters of the water of Yansai lake. The animal-like stone and overhanging cliff create 18 beautiful sceneries which win the name of “miniature of Guilin in north China” for the lake.
With Changshou Mountain to the east, Reunion Temple, warm spring, Baizhuangzi, Hou Temple to the north, peach valley to the northeast, and frontier provinces to the southwest, Yansai lake in winter is a good place for travel. In winter, the lake is a paradise for fisherman. Digging the ice and taking a small fishhook into the hole, the fish will be caught continuously.
The island in the center of lake is named “sword peak of cave Mountain”. Two branches of water converge at the front of the mountain, forming a deep pool. Above the pool is a natural stone cave on the mountainside, which is a haunt for snakes. Below the pool is an abyss, beside which is the path leading to the top of the mountain. Legend has it that this cave is the place where god Lv dongbin fought the dragon. Because of the rising of water level, more than half of the mountain and cave were submerged, only emerged the island and “sword blade” for visiting.