The horizontal stone chamber of the Asuka Period discovered in the Kodayama burial mounds was unparalleled by featuring the arched ceiling structure, created based on the skills and techniques imported from China.
This stone chamber was achieved by adopting state-of-the-art domestic stone chamber construction technology, such as Kagite-zumi (hook-pattern stonework) technique that prevented displacement of the stones.

Historic Park
Stone chamber of the Kodayama burial mounds
In the Kodayama burial mounds, two rectangular tombs were confirmed to have been constructed during the Asuka Period. Both of them have horizontal masonry tuff stone chambers constructed using local Ugawa stone. The ceiling is lost, but the rising part toward the ceiling is arched. Thus, this stone chamber is considered to have had an arched ceiling. In the Kodayama Burial Mounds Museum, one was reproduced and is currently exhibited within the museum, and the other was transferred to and restored within the historic park.

Archaeological Material
Excavated articles from the Kodayama Burial Mounds
The articles excavated from the Kodayama burial mounds are considered to be from the Early and Late Kofun (Tumulus) Period and the Asuka Period. Those articles, collected from stone chambers including ornaments of cylindrical stone beads and curved jewels, are stored and exhibited at the Kodayama Burial Mounds Museum.