"Japan's largest stone circles aligned to the summer solstice sunset, 4,000 years old"
Ōyu Stone Circles
Kazuno, Akita Prefecture, Japan
On a plateau above the Oyu River in northern Japan, two stone circles have watched the summer solstice sun set along the same axis for 4,000 years. The Manza circle spans 46 meters; the smaller Nonakado reaches 42 meters. Both contain sundial-like stonework pointing to the moment when the year's longest day ends. For the Jomon people who built them, these circles served as cemetery, calendar, and place of ceremony where earth and sky aligned.
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Quick Facts
Location
Kazuno, Akita Prefecture, Japan
Tradition
Site Type
Coordinates
40.2735, 140.8051
Last Updated
Jan 21, 2026
The Oyu Stone Circles were constructed by Jomon people during the Late Jomon period, approximately 2000-1500 BCE. This was a time of increasing ceremonial complexity across northern Japan, with stone circles appearing at many sites. Oyu represents the largest and most astronomically sophisticated of these, demonstrating that the Jomon tracked solar cycles and encoded this knowledge in monumental architecture.
Origin Story
No written records exist from the Jomon period. What we know of Oyu comes from the stones and material culture preserved at the site, interpreted through archaeological methods.
The Jomon people lived in the Japanese archipelago for over 10,000 years, developing sophisticated cultures while maintaining a hunter-fisher-gatherer economy. The Late Jomon period, when the Oyu circles were built, saw increasing investment in ceremonial architecture, with stone circles appearing across Hokkaido and northern Tohoku.
The selection of this location—a plateau on the left bank of the Oyu River—was deliberate. The Jomon flattened the natural terrain to create the level surface required for the circles' precise geometry. They then brought stones from elsewhere, arranging them in the double-circle pattern with sundial-like central features oriented to the summer solstice.
The construction of the Manza circle, with its 46-meter diameter and over 100 stone arrangements, required sustained community effort. Generations participated in building, maintaining, and using this sacred space. The dead were buried within the circles, their graves marked by stones, their remains integrated into the pattern of the whole.
Spiritual Lineage
Oyu belongs to the Late Jomon tradition of stone circle construction that produced similar sites across Hokkaido and northern Tohoku. The Isedotai Stone Circle in the same region, the Komakino Stone Circle in Aomori, and other sites demonstrate shared practices for marking sacred ground and observing celestial events. No continuous tradition connects to the Jomon practices at Oyu. The Jomon population gradually gave way to later peoples and cultures. Yet the patterns visible here—solar observation, ancestor veneration, the marking of sacred ground with stone—anticipate themes in later Japanese religious traditions. The archaeological study of Oyu began with its discovery in 1931 and continues through its role in the UNESCO World Heritage property. The site contributes to scholarly understanding of Jomon astronomical knowledge and ceremonial practices.
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