Location and Historical Significance
The burial mound stands on a ridge in the southern part of the Tokushima Plain, on the left bank of the Tatara River, which belongs to the Katsura River system. Several groups of ancient burial mounds are scattered throughout the lower Katsura River basin, and Shibuno Maruyama Kofun is regarded as the principal mound of the local Shibuno Kofun Group.
The site was documented in the Katsura District Gazetteer in 1923. Archaeological investigations carried out from fiscal year 1999 onward gradually revealed more about its structure and historical importance.
The mound faces west, with a rectangular front section extending from its circular rear section. Both sections were built in three tiers, demonstrating the considerable labor and organizational resources required for its construction. Its size and design suggest strong cultural influences from the Kinai region, the area around present-day Nara, Kyoto, and Osaka that was an important center of political power in ancient Japan.
Structure of the Burial Mound
Dimensions and Layout
The main mound measures approximately 105 meters in total length. Including the surrounding moat, the entire monument extends about 118 meters. Its principal dimensions are as follows:
Overall length, including the moat: Approximately 118 meters.
Mound length: Approximately 105 meters.
Circular rear section: Approximately 69 meters in diameter and 18 meters high, constructed in three tiers.
Rectangular front section: Approximately 59 meters wide and 16 meters high, also constructed in three tiers.
Narrow connecting section: Approximately 44 meters wide.
The surrounding moat follows an asymmetrical course around the mound. This feature forms part of the monument’s overall design, and the mound and moat together remain in relatively good condition.
Stone Covering and Haniwa Figures
The mound’s exterior was covered with fukiishi, stones placed over the earthen surface to protect it from erosion and create a distinctive finish. Rows of cylindrical haniwa clay objects were also arranged around the mound.
Archaeologists have identified several types of haniwa, including cylindrical and wide-mouthed, flared forms resembling morning-glory flowers, as well as figures shaped like houses, shields, and boats. These objects provide valuable evidence of the rituals and beliefs associated with elite burials during the Kofun period.
The Unique Southern Projection
One of the site’s most distinctive features is a small projecting platform known as a tsukuridashi, located on the southern side of the mound. Measuring approximately 12 meters wide, 5 meters deep, and 2 meters high, this feature is particularly significant because it is the only example of its kind identified at a burial mound in Shikoku.
Excavations in this area uncovered numerous small jars and fragments of haniwa. These finds offer important clues about ceremonial practices and the ways objects were used in funerary rituals during the fifth century.
The Burial Chamber and the Summit
The exact location and structure of the burial chamber have not been confirmed because the rear section of the mound has not been excavated. However, local accounts report that a large ceiling stone was once observed at the site.
Ground-penetrating radar surveys have also detected a depression that may indicate a looters’ pit, along with signals suggesting the possible presence of an east–west-oriented stone chamber. The suspected chamber measures approximately 5 meters wide and 2.5 meters long, although its nature remains unconfirmed.
A stone monument, or itabi, said to have once stood on the summit of the circular rear section is preserved at Chōsō-ji Temple in Shibuno-cho, Tokushima City. Its association with the mound suggests that the site continued to hold religious or symbolic significance in later periods.
History of Shibuno Maruyama Kofun
The Rise of the Katsura River Basin
During the earlier Kofun period, large burial mounds were actively constructed in areas such as Naruto, Itano, and Mount Kiyonobu in present-day Tokushima Prefecture. As time passed, mound construction expanded into the lower Katsura River basin.
Shibuno Maruyama Kofun emerged as a particularly prominent monument in this developing landscape. Its scale and architectural characteristics indicate that the people who commissioned it had considerable authority and maintained cultural connections with the powerful communities of the Kinai region.
The mound is considered especially important for understanding the changing balance of power in the ancient Awa region, which broadly corresponds to present-day Tokushima Prefecture. It is also regarded as the last major keyhole-shaped burial mound built in the prefecture, marking an important transition in the region’s ancient burial traditions.
Archaeological Research and Historic Designation
After its appearance in the Katsura District Gazetteer in 1923, the site was designated a Tokushima Prefectural Historic Site in 1953. An excavation associated with the relocation of nearby residences was carried out in 1988, helping researchers better understand the extent and significance of the mound.
Between 1999 and 2005, the Tokushima City Board of Education conducted several archaeological investigations. These studies examined the mound’s structure, surrounding moat, and the arrangement of haniwa. Additional radar surveys were conducted by the Nara National Research Institute for Cultural Properties in 2002 and by the University of Toyama in 2005. The results suggested the possible presence of a burial facility within the rear section.
Following these investigations, Shibuno Maruyama Kofun was designated a National Historic Site in 2009. The protected area was expanded in 2012 to provide further protection for this important archaeological heritage.
Conservation and Preservation
Preservation and restoration projects were carried out from 2013 to 2016 and again from 2017 to 2019. These projects were based on archaeological findings and included measures to protect the mound from weathering, erosion, and structural damage.
Such conservation work helps safeguard the site for future generations and ensures that this important part of Tokushima’s ancient history remains protected.
Discover Ancient Tokushima
Shibuno Maruyama Kofun is a remarkable destination for travelers interested in Japanese archaeology and the origins of regional society. Its imposing scale, three-tiered construction, distinctive southern projection, and surviving traces of haniwa reveal the sophistication of burial practices during the fifth century.
As the largest ancient burial mound in Tokushima Prefecture, the site also provides a valuable perspective on the region’s relationship with the powerful political and cultural centers of ancient Japan. Exploring this National Historic Site offers an opportunity to connect with a distant past and appreciate the archaeological heritage of Tokushima.