The first buttress dam built in Japan in 1923, it is recognized as a Civil Engineering Heritage site. The front yard plaza is covered with grass and is a popular place for citizens to enjoy cherry blossoms in spring and autumn leaves in fall.

The Sasaryu Dam was the first buttress dam in Japan, built in 1923. The buttress dam was a lightweight dam with a structure in which the wall surface subject to water pressure was supported by a lattice of auxiliary walls (fusible walls), a design method that saved on concrete, which was expensive at the time. It has long been known as the "water source of the Aka River" and continues to serve as a water reservoir for Hakodate residents today. It was renovated in 1985. The dignified appearance of the towering structure gives it a sense of beauty.

Visitors can climb up to the embankment from the side and see up close the beautiful blue water behind this wall. The water surface is high and powerful.
The front yard plaza of the dam has been developed as a grass-covered park and is a place of relaxation for Hakodate citizens. In addition to picnics and sports, the park is a popular spot for cherry blossoms in spring and autumn leaves in fall. The park is located on high ground in the Akagawa district, about 15 minutes by car from downtown Hakodate.