Iyo Kokubunji Tower Ruins: Where a Sixty-Meter Eighth-Century Pagoda Once Stood
On a square earthen platform in a residential corner of Imabari, thirteen weathered granite stones still hold the position once occupied by an enormous seven-story pagoda. The platform measures 17.4 meters on each side. Each stone weighs hundreds of kilograms; each was cut, dragged, and set into place sometime in the middle of the 700s. Above them once rose a wooden tower that may have reached sixty meters — taller than most Japanese buildings until well into the twentieth century. The tower burned in the year 939. The stones did not.
These are the surviving foundations of Iyo Kokubunji, the provincial temple commissioned by Emperor Shōmu (701–756) for ancient Iyo Province. The site was designated a National Historic Site (shiseki) on March 3, 1921, among the earliest such designations after Japan's Historic Sites, Places of Scenic Beauty, and Natural Monuments Preservation Law of 1919.
An Imperial Network of Provincial Temples
In 741, Emperor Shōmu issued an edict from the new capital at Heijō-kyō (Nara) ordering every province to establish two temples: a kokubunji for monks and a kokubunniji for nuns. The country had suffered a smallpox epidemic that decimated the political elite, a major rebellion in Kyushu, and famine. Buddhism, the emperor calculated, would protect the state. Each provincial temple was to house a copy of the Konkōmyō Saishōō-kyō (Golden Light Sutra), and each was required to construct a seven-story pagoda.
Iyo Province, on the northwestern coast of Shikoku, complied. The chosen site sat in what is now Imabari City, on flat land between two small hills, with the provincial administrative center (kokufu) located about 1.8 kilometers to the northeast. Construction proceeded through the middle and later eighth century. The temple was supported by local elites: contemporary records preserved in the Shoku Nihongi mention that in 749, a man named Ōshi no Atae Kamatari from Uwa District donated goods and helped fund the temple's Buddha image, and was rewarded with an official court rank.
By the end of the Nara period (710–794), the complex stood complete — main hall, lecture hall, monks' quarters, and the towering seven-story pagoda whose foundations remain.
What the Stones Tell Us
The pagoda's design followed a strict canonical layout. At the center sat the shinso, the foundation stone for the central pillar that ran the full height of the structure. Around it, four stones supported the inner four pillars (shitenbashira) that framed the central bay. Beyond these, sixteen more stones (four on each side of the tower's footprint) supported the outer pillars, with three intercolumniations across each face of the square plan.
Excavations by the Ehime Prefectural Board of Education in 1968 confirmed the platform's dimensions and recovered approximately twelve to thirteen stones, of which only four remained in their original positions. The platform itself, a square 58 shaku (17.4 meters) per side and 1.2 meters tall, was constructed by the hanchiku method: layers of red clay and sandy soil tamped down in nine distinct strata, each compacted by foot or wooden pestle. A trench dug into the east side of the platform during the excavation exposed about 70 centimeters of this layered construction.
The pillar spacing offers a quiet detail of architectural sophistication: the central bay measures 12 shaku (about 3.6 meters), one shaku wider than each flanking bay of 11 shaku (3.3 meters). This subtle widening of the central interval mirrors the techniques used at Kōfuku-ji and Gangō-ji, the major eighth-century temples of the Nara capital, suggesting that craftsmen working in Iyo were drawing on metropolitan models. Based on the relationship between the central foundation stone's diameter and the pagoda's footprint, scholars estimate the tower stood seven stories tall, perhaps 65 meters in total height.
Four Fires, Eleven Centuries
The pagoda did not survive the medieval period. According to temple records, the original Iyo Kokubunji suffered destruction four times by fire. The first came in 939, during the rebellion led by Fujiwara no Sumitomo, a former government official who turned pirate and laid waste to Shikoku's coastal provinces. The temple was rebuilt at reduced scale, only to burn again in 1184 during the Genpei War. A third fire came in 1364, when Hosokawa Yoriyuki's forces from Sanuki swept through Iyo during the Nanboku-chō conflict. The fourth and final destruction occurred in 1584, when Chōsokabe Motochika of Tosa invaded Iyo and burned what remained.
By 1689, the monk-scholar Jakuhon noted in his Shikoku Henrei Reijōki that nothing stood at the site except a small thatched hall. Serious rebuilding began only in the late Edo period; the current main hall of nearby Iyo Kokubunji dates to 1789. Through all of this, the granite foundation stones of the original pagoda — heavy, low to the ground, fundamentally unburnable — endured.
What to Look For at the Site
The ruins occupy a small fenced plot of roughly a hundred square meters, surrounded on three sides by private houses and approached from a narrow lane. A stone marker inscribed with the characters Shiseki Iyo Kokubunji Tō Shi (Historic Site, Iyo Kokubunji Tower Ruins) stands near the entrance. The platform itself is partly grass-covered; the stones sit upon and beside it, some upright, some leaning, several relocated from their original positions during centuries of disturbance.
The central pillar foundation, the largest of the visible stones, is the easiest to identify: a roughly cylindrical granite block with a flattened circular seat where the wooden central pillar once rested. Other stones display similar circular pillar seats, sometimes with a small projecting tenon at the center designed to anchor the post above. This detsuko-style seating was standard in eighth-century pagoda construction.
Stand at the center, look up, and try to picture the scale: a tower the height of a twenty-story modern building, its roofs sweeping outward in seven tiers, dominating a landscape where the tallest other structures were single-story houses and the surrounding hills.
The Living Successor: Iyo Kokubunji Today
About 100 meters west of the tower ruins stands the present Iyo Kokubunji, which traces its institutional descent from the eighth-century original. The temple is the fifty-ninth station on the Shikoku Pilgrimage, the 1,200-kilometer route visiting eighty-eight temples associated with the monk Kūkai (774–835). Kūkai himself is said to have spent a period of residence at the original Iyo Kokubunji, donating a painting of the Five Great Wisdom Kings.
The temple grounds today are modest but well-kept. The main hall, rebuilt in 1789, houses the principal image of Yakushi Nyorai (the Medicine Buddha). A black ceramic vessel called the Yakushi no Tsubo stands in the courtyard; pilgrims touch it while reciting Yakushi's mantra in hopes of healing. Several pieces of Heian and Kamakura period statuary, along with ancient roof tiles excavated from the original temple grounds, are preserved in the temple's storehouse.
The Wider Heritage Landscape
Imabari and its surroundings hold remarkable historical depth beyond the tower ruins. About 1.3 kilometers south of the ruins lies the suspected site of the Iyo Kokubunniji, the provincial nunnery commissioned alongside the monks' temple in the same imperial edict, now identifiable only by ancient roof tiles found beneath what is today Sakurai Elementary School. The administrative seat of ancient Iyo Province (the kokufu) is thought to have stood about 1.8 kilometers northeast in the Kamitoku district, although the exact location has yet to be confirmed by excavation. Together, these three sites (temple, nunnery, and government office) outline the layout of an early Japanese provincial capital.
Travelers may also wish to visit the nearby memorial to Wakiya Yoshisuke, a fourteenth-century general of the Southern Court who died at Iyo Kokubunji in 1342. The Shimanami Kaidō, the cycling route connecting Honshu and Shikoku across six islands of the Seto Inland Sea, passes through Imabari, and the magnificent Ōyamazumi Shrine on Ōmishima island lies about 25 kilometers to the north.
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Q&A
- Can I visit the site freely, and is there an admission fee?
- Yes. The tower ruins are an open-air heritage site with no fence, gate, or admission fee. They can be visited at any time of day, although early morning or late afternoon offers the best light for photography. There is no visitor center on site.
- How do I reach the site from Imabari Station?
- From the Imabari Station front bus stop, take the Setouchi Bus on the Sakurai-Danchi Junkan line (about 22 minutes) and get off at Kokubunji. The current Iyo Kokubunji is a three-minute walk; the tower ruins lie a further 100 meters east. By car from Imabari IC, the journey takes about 20 minutes.
- How tall was the original pagoda, and why don't we know the exact height?
- The tower no longer exists; no contemporary drawing or specification survives. Researchers estimate its height by extrapolation from the surviving central foundation stone, applying ratios derived from similar pagodas elsewhere. The most widely cited figure is about 60 to 65 meters, and the tower is believed to have had seven stories, matching the standard set by Emperor Shōmu's 741 edict.
- How many stones remain, and are they in their original positions?
- Visitor materials commonly cite thirteen surviving stones, including the central foundation stone. The 1968 prefectural excavation confirmed that only four of these are still in their original positions; the others were moved at various points over the centuries, though all are believed to be original to the eighth-century construction.
- What is the relationship between the tower ruins and the current temple of the same name?
- The current Iyo Kokubunji, located about 100 meters west of the ruins, is the institutional successor of the eighth-century temple but stands on a slightly different site. The present main hall dates to 1789; the original temple complex, including the pagoda, occupied the area around the ruins. The current temple is the fifty-ninth station of the Shikoku Pilgrimage.
Basic Information
| Name | Iyo Kokubunji Tower Ruins (伊予国分寺塔跡) |
|---|---|
| Location | Kokubu, Imabari City, Ehime Prefecture |
| Designation | National Historic Site (designated March 3, 1921) |
| Designation criterion | Sites of shrines and temples and other places relating to religious practice |
| Period | Nara period (mid-8th century) |
| Site features | Square earthen platform 17.4 m per side; approximately 13 granite foundation stones surviving, including the central pillar stone |
| Estimated original tower | Seven-story pagoda, approximately 60–65 m in height |
| Excavation | Surveyed by Ehime Prefectural Board of Education in 1968 |
| Access | From Imabari Station, Setouchi Bus (Sakurai-Danchi Junkan or Karako-dai Junkan line) to Kokubunji stop, then 3-minute walk plus 100 m east of present Iyo Kokubunji; from Imabari IC, about 20 minutes by car |
| Admission | Free; open at all times |
| Nearby | Iyo Kokubunji (Shikoku Pilgrimage Station 59), Iyo Kokubunniji site, Iyo Kokufu site (presumed), Wakiya Yoshisuke memorial |
References
- 国指定文化財等データベース「伊予国分寺塔跡」 (Agency for Cultural Affairs)
- https://kunishitei.bunka.go.jp/bsys/maindetails/401/2536
- 文化遺産オンライン「伊予国分寺塔跡」 (Cultural Heritage Online)
- https://bunka.nii.ac.jp/heritages/detail/211270
- えひめの記憶『愛媛県史 原始・古代Ⅰ』「伊予国分僧寺」 (Ehime Prefectural History)
- https://www.i-manabi.jp/system/regionals/regionals/ecode:2/61/view/7729
- 今治市公式観光情報「国分寺（四国霊場59番札所）」 (Imabari City Tourism)
- https://www.city.imabari.ehime.jp/kanko/spot/?a=130
- 四国八十八ヶ所霊場会「第59番札所 金光山 最勝院 国分寺」 (Shikoku 88 Temple Pilgrimage Association)
- https://88shikokuhenro.jp/59kokubunji/
Last verified: 2026.05.18