Kasori Shell Mound is a major archaeological site in Sakuragi, Wakaba Ward, Chiba City, Chiba Prefecture. The site consists of a large ring-shaped settlement from the Jomon period, together with extensive shell mounds created by the people who lived here thousands of years ago.
It is one of the largest Jomon shell mound sites in Japan and is regarded as an extremely important archaeological site for understanding prehistoric life and culture. The North Shell Mound was designated a National Historic Site in 1971, followed by the South Shell Mound in 1977. In 2017, the entire site was elevated to the status of a Special Historic Site of Japan.
Today, Kasori Shell Mound is an important cultural heritage site where visitors can learn about the daily lives, environment, and beliefs of people who lived in the Japanese archipelago thousands of years ago.
Kasori Shell Mound is situated on a plateau approximately 2 kilometers north of the Sakatsuki River, a tributary of the Miyakogawa River that flows through Chiba City.
The archaeological site extends across a tongue-shaped plateau measuring approximately 500 meters east to west and 800 meters north to south. Its enormous scale makes it one of the world’s largest shell mound sites.
The site consists primarily of two major shell mounds: the North Shell Mound and the South Shell Mound. The North Shell Mound has a diameter of approximately 130 meters and forms a ring shape, while the South Shell Mound measures approximately 170 meters along its longer axis and has a horseshoe shape.
Because the two shell mounds are connected, their overall configuration resembles the shape of the number 8. This distinctive layout provides important evidence of the complex structure of Jomon settlements.
Remains of dwellings dating back approximately 7,000 years have been discovered at Kasori Shell Mound. These discoveries show that people were already living in the area during the Jomon period and making use of the abundant natural resources around them.
Large-scale shell mound formation began approximately 5,000 years ago, during the middle Jomon period. Layers known as disposal zones gradually accumulated shells, broken pottery, and other discarded materials.
Over a period of approximately 1,000 years, these accumulated materials formed enormous ring-shaped shell mounds. They provide an unusually detailed record of everyday life in prehistoric Japan.
The North Shell Mound was formed during the Middle Jomon period, approximately 5,000 to 4,000 years ago. It has a diameter of about 130 meters and forms a large circular shell mound.
In its earliest stage, the area contained relatively small shell deposits and dwellings. Over time, shells, pottery fragments, and other discarded materials accumulated around the residential area.
This process eventually created the enormous ring-shaped mound that can be seen as part of the archaeological remains today.
During the Late Jomon period, approximately 4,000 to 3,000 years ago, use of the North Shell Mound gradually declined, and a new settlement and shell mound developed farther south.
The South Shell Mound has a horseshoe-shaped configuration and measures approximately 170 meters along its longer axis. Like the North Shell Mound, it was formed through the repeated disposal and accumulation of shells, pottery fragments, and other materials.
Animal remains have also been discovered here, including the bones of dogs buried together with humans. These discoveries provide valuable clues about the relationship between people and animals during the Jomon period.
Kasori Shell Mound was first introduced to the academic world in 1887. At the time, the Japanese Anthropological Society described it as one of the most important shell mound sites in Japan.
A major preservation movement began in 1963, when part of the land was purchased by a private company for development. Local teachers, archaeologists, and residents organized efforts to protect the archaeological site from being destroyed.
The preservation campaign received broad support from citizens. Eventually, Chiba City purchased the land, allowing Kasori Shell Mound to be protected as an important cultural asset belonging to the community.
In 1964, Chiba City decided to develop the land around the North Shell Mound as a park. In 1971, the site was designated a National Historic Site under the name Kasori Shell Mound.
The South Shell Mound was added to the designation in 1977. Then, in 2017, Kasori Shell Mound became the first shell mound site to be designated a Special Historic Site of Japan.
This highest level of national historic-site protection reflects the exceptional archaeological importance of Kasori Shell Mound and its value as a source of information about Jomon culture.
The Chiba City Kasori Shell Mound Museum stands within the archaeological park and displays artifacts excavated from the site. Exhibits include Jomon pottery, stone tools, animal bones, and other archaeological remains.
The museum opened in 1966 and has played an important role in introducing the history and culture of Kasori Shell Mound to local residents, students, and visitors.
The museum building has aged considerably, and its location within the Special Historic Site has also created restrictions on rebuilding the existing structure.
The existing building is therefore scheduled to be demolished and replaced by a new museum at a different location. The new facility is planned to reopen in 2027, with expanded exhibitions designed to provide visitors with a deeper understanding of Kasori Shell Mound and Jomon culture.
Kasori Shell Mound Park hosts regular events and programs that allow visitors to learn about and experience aspects of Jomon life. These activities provide an engaging way to understand the archaeological remains beyond simply viewing them.
Ongoing preservation and research activities are also an important part of the site. The park serves not only as a historical attraction but also as a place for education and cultural heritage preservation.
The nearest station is Sakuragi Station on the Chiba Urban Monorail Line 2. The archaeological site is approximately a 15-minute walk from the station.
Kasori Shell Mound is one of Japan’s most significant archaeological sites for understanding the Jomon period. Its enormous scale, distinctive ring and horseshoe-shaped shell mounds, and wealth of archaeological remains provide a rare glimpse into the lives of people who lived in the region thousands of years ago.
The site’s history is also notable because its preservation was made possible through cooperation between local residents, teachers, archaeologists, and Chiba City. Their efforts prevented the site from being lost to development and helped preserve it for future generations.
For visitors interested in Japanese history, archaeology, ancient cultures, and traditional ways of life, Kasori Shell Mound offers an opportunity to step far beyond the modern city and discover the deep prehistoric roots of Chiba.