The Sasayama site is the remains of a circular settlement from the middle to late Jomon period. Between 1980 and 1985, excavations were carried out in conjunction with the construction of a municipal baseball stadium, an athletics stadium, and other facilities. In 1999, 57 pieces of deep bowls, including 14 flame-style pottery artefacts and 3 crown-like pottery artefacts, were designated as National Treasures for the first time as Jomon earthenware.
Flame-style pottery represents the middle Jomon period in Niigata Prefecture and is excavated together with crown-like pottery. Due to its almost excessive three-dimensional decoration, the pottery is considered to be a ceremonial pot rather than a daily necessity. In addition to flame-style pottery and crown-like pottery, there are: [1] earthenware characteristically found in the Shinano River basin; and [2] earthenware that looks influenced by the cultures of the Hokuriku, Tohoku, and Kanto regions.
In addition, a total of 871 items are designated as National Treasures, including: [1] shallow bowls, clay figurines and other clay products; [2] stone arrowheads, stone axes, and other stone tools; and [3] pendants, stone rods, and other stone products.