長岡市
The Shinano River Project, funded by the British Academy, investigates the development of the Shinano—Chikuma River system. It has uncovered some of the earliest examples of Flame-style pottery (kaen doki), dating from the Middle Jōmon period (3500–2500 BCE), have been found at Sanka excavation site in Nagaoka, Niigata, near the confluence of the Sai and Shinano Rivers.