Tsuda Kofun Cluster

The Tsuda Kofun Cluster (津田古墳群) is a group of nine burial mounds in Sanuki, Kagawa Prefecture, on the island of Shikoku in Japan. The mounds occupy an area of 4.5 kilometers east–west and 3.5 kilometers north–south, centered on the coast of Tsuda Bay overlooking the Seto Inland Sea. They were built from the early Kofun period to the early middle Kofun period.

The earliest mounds are built from piled stones in a style unique to eastern Shikoku and face east. Later tumuli contain cylindrical haniwa and are oriented north–south. The site also has split bamboo-shaped sarcophagi made from volcanic stone produced in the area. Similar stone sarcophagi have been found in the Kinai, Kibi, and Awa regions, which suggests a strong maritime connection.

The cluster was known in the Edo period, and archaeological excavations have been recorded from the early twentieth century onwards. It was designated a National Historic Site in 2013, and the protected area was expanded in 2014. Construction of burial mounds at Tsuda stopped when the larger Tomita Chausuyama Kofun appeared inland, indicating a major political consolidation in the region.

Monuments of this kind in Japan were built mainly between the middle of the third century and the early seventh century CE, and the period takes its name from them. The most distinctive form is the keyhole-shaped mound (zempō-kōen-fun), with one square end and one round end seen from above, but plain round mounds, double-rectangle mounds, and square mounds also occur.

The National Historic Site consist of nine burial mounds that were built from the early Kofun period to the early middle Kofun period in an area of 4.5 kilometers east–west and 3.5 kilometers north–south centered on the coastal area of Tsuda Bay overlooking the Seto Inland Sea. This group of burial mounds was known in the Edo period, and there are records of archaeological excavations from the early twentieth century onwards. The earliest mounds are made from piled stones in a style unique to eastern Shikoku and are orientated to the east; however, later tumuli contain cylindrical haniwa and are orientated in a north–south direction. This indicates increasing political and cultural influences from the Kinai region. The split bamboo-shaped sarcophagi at the Tsuda Kofun cluster was made from volcanic stone produced in this area, and the same volcanic stone sarcophagus have been found in the Kinai, Kibi, and Awa regions, which suggests a strong maritime connection. In the middle of the Kofun period, when the Tomita Chausuyama Kofun, the largest keyhole-shaped burial mound in Shikoku, appeared inland, the construction of burial mounds in the Tsuda site stopped. This clearly shows that a major political consolidation that occurred in the region during that period.