A dam lake that dammed up the northernmost long river "Teshio River". The Iwaonai Great Bridge, which crosses the lake brimming with water, shines on the lake surface, and a wonderful harmony of nature and artificial forms can be seen, and in the surroundings, there are campsites and bungalows, and at the lake, you can enjoy fishing, canoeing, boating, etc.

"Erica Park" adjacent to Iwaonai Lake. "Erica" is a plant of the Ericaceae family, mainly originating from Africa and Europe. In this park, including "Erica" and "Calluna," a relative of Erica, 60,000 plants of 11 varieties that adapt to this region are planted. Lovely flowers of about 1 centimeter bloom densely, and can be appreciated from around June until around September.