History and Origins
Construction During the Nara Period
Doto was constructed within the grounds of Onoji Temple, one of the 49 temples and monasteries traditionally associated with Gyoki in the early Nara period.
According to the Gyoki Nenpu, a record of Gyoki’s activities, construction of the monument began in 727, when Gyoki established Onoji and Ono Nijiin. A medieval illustrated biography of Gyoki, the Gyoki Bosatsu Gyogyo Eden, also depicts a finial and jewel at the top of the monument and refers to a 13-tiered earthen pagoda at Onoji.
The History and Revival of Onoji Temple
Onoji Temple was destroyed by fire during the Muromachi period and was later rebuilt during the Edo period. The present temple belongs to the Shingon school of Buddhism, and its main hall dates from the middle of the Edo period.
The present temple grounds are relatively small and no longer convey the scale of the original complex. However, foundation stones from the temple’s founding period remain on the grounds, suggesting that Onoji was once a substantial Buddhist institution.
Geographical Features of Doto
Doto stands in the former Haji District, now Tuchi-cho, on a plateau in the Semboku Hills. The area was historically considered difficult to supply with water.
The monument stands on a hill approximately 50 meters above sea level, with good visibility toward the south. These geographical conditions are thought to have influenced the location and character of the Buddhist monument.
National Historic Site and Preservation
Discovery and Historic Site Designation
Research into Doto began in earnest after inscribed roof tiles were discovered around the site in the early Taisho period.
Part of the privately owned site was damaged in 1946. In response, the Osaka Prefectural Board of Education conducted an emergency investigation and provisionally designated the site as a historic site in 1952.
The investigation established that Doto was not a burial mound but a Buddhist monument. In 1953, it was officially designated as a National Historic Site.
Archaeological Investigations
Archaeological excavations and preservation work were carried out between 1997 and 2003. These investigations revealed important information about the monument’s original form and construction.
The sides of Doto are precisely aligned with the cardinal directions. Its foundation measures approximately 53.1 meters on each side, while its original height is estimated to have been at least 8.6 meters.
Archaeological evidence has also revealed a distinctive shape influenced by Buddhist stupas originating in India, making Doto a particularly unusual example of Buddhist architecture in Japan.
Structure and Construction Techniques
A 13-Tiered Step Pyramid
Doto has the form of a 13-tiered stepped pyramid with a square pyramidal structure and a flat top.
Excavations revealed that the depth of each tier becomes progressively narrower toward the upper levels. This design created a visual effect that made the relatively low monument appear taller and more imposing.
Roof Tiles and the Tile Kiln
Large quantities of roof tiles were used throughout the different levels of Doto. A tile kiln was discovered approximately 170 meters northwest of the monument.
Known as the Onoji Tile Kiln, the site provides valuable evidence of how roof tiles were produced and used to decorate Buddhist buildings during the period.
Excavated Artifacts and Their Importance
Nationally Designated Cultural Properties
A total of 1,171 artifacts dating from the Nara period through the Edo period have been excavated from Doto, including roof tiles and painted materials.
Among them, 1,082 items have been designated as National Important Cultural Properties.
Some of the roof tiles bear inscriptions such as “Year 4 of the Jinki Era” and “Year 5 of the Jinki Era.” These inscriptions provide valuable clues about the construction date and later restoration history of the monument.
Inscribed Roof Tiles
Some of the excavated tiles contain the names of people and prayers or dedicatory texts. These inscriptions provide information about the people involved in the construction of the site and offer valuable insight into Buddhist beliefs and community participation during the Nara period.
Gyoki, Irrigation, and Regional Development
The Connection Between the Irrigation Pond and Doto
Archaeological research has revealed a close relationship between Gyoki’s regional development projects and the construction of Doto.
Komoike Pond, located north of Doto, is believed to have been created by Gyoki as an irrigation reservoir. The pond helped support agricultural production in the surrounding area by improving access to water.
Supporting Local Life Before Building Religious Sites
According to the Gyoki Nenpu, irrigation facilities were developed in the Haji area before Doto was constructed. The temple and Buddhist monument were then established afterward.
This suggests that Gyoki’s activities combined community development and Buddhist teachings. By first improving the foundations of everyday life for local residents and then establishing temples and Buddhist monuments, he helped connect religious activities with practical improvements to the surrounding community.
A Rare Example of Buddhist Heritage in Japan
Doto at Onoji Temple is a remarkable monument where Nara-period Buddhist faith, architectural innovation, and regional development came together.
Its unusual stepped-pyramid form, archaeological discoveries, inscribed roof tiles, and connections with Gyoki provide valuable insight into the religious and social history of 8th-century Japan.
The monument is also notable for its apparent connection with Buddhist architectural traditions originating in India, making it an unusual surviving example of how Buddhist culture was adapted within ancient Japan.
Today, Doto remains carefully preserved in Naka Ward, Sakai, allowing visitors to encounter an important part of Japan’s ancient Buddhist and archaeological heritage.