There's nothing more calming than sitting beside a river and watching the water as it flows downstream. Why not pack a picnic and spend a quiet couple of hours at Nagatoro Iwadatami?
To explore this flowing body of water, head to Nagatoro. There are loads of other worthwhile attractions in this area, like Chichibu Nagatoro Hodosan Shrine, Saitama Museum of Rivers, and Saitama Museum of Natural History.