Gassan Dam is one of the tallest Dam in Tohoku region. It is located in Tsuruoka city, Yamagata Prefecture. The height of the dam is 123m and 393m wide. The artificial lake is called Lake Asahi Gassan. It is built for the flood control. It is also used for generating the electricity.

The office has the small aquarium that displays the fishes of this dam.

In the Dam Tour, you can enter the dam and see the gate and the wire of the gate. You can also access to the bottom of the dam to see it from the bottom. It is only available when the dam is releasing the water.

The Dam release the water around April to May when the water from the melted snow from the mountain is coming into the dam. Also, before the rainy season, the release the water.