The Mizuko Shell Midden is located at the eastern end of the Kawagoe Plateau, which is surrounded by the Shingashi River and the Iruma River, in the northern part of the Musashino Plateau in the western part of the Kantō Plain. Although the area is now a considerable distance inland from the coast of Tokyo Bay, during the Jōmon period it was a peninsula on a long inlet of the sea. The shell mound was discovered in 1917. In subsequent surveys, including an archaeological excavation conducted in 1978, it was determined that the midden was a shell ring with a diameter of 160 meters, consisting of 67 smaller shell middens. Each mound consisted primarily of fresh and brackish water shellfish (Yamato-shjimi), and were built on top of the sites of pit dwellings. It is a type site for a unique style of Jōmon pottery called the "Mizuko-type pottery".
