Lake Okuchichibu Momiji (奥秩父もみじ湖, okuchichibumomijiko) is dam lake with Takizawa dam. It is located in Okuchichibu, Sasitama prefecture. It was completed by 2008. There are many view spot for watching the dam. Because it is part of Nakatsu valley, in the fall, you can enjoy great autumn tint. The name of the lake is named for that.
Tourist info.
There is parking and restroom.
Access
0. at Omiya Station
1. use JR Shonanshinjuku Line to Kumagaya (30 min.)
2. use Chichibu Line to Sanpoguchi (40 min.)
3 use local bus to Takizawa Dam (40 min.)
20 min
New Wave Samurai Movie. 
映画好き集まれ！ 
One of the best spot where you can enjoy Autumn leaves. Currently, because the natural resource has been changed by the completion of the dam, people start planting new trees which grows great around dam lake. Also, not just putting new plants, their activities are preserving the original beauty of the Nakatsu river. In the near future, this will be also count as the best landscape.
Hight: 140m
Width: 440m
Size 108.6km