Marukoyama Kofun

The tumulus stands at the southern end of the Mayumi Hills, in the western part of Asuka Village, and is surrounded by other tombs from the end of the Kofun period, such as Takamatsuzuka Kofun and Kengoshizuka Kofun. It was built on a flattened area on the southern slope of a ridge running east to west, and has a diameter of 15 meters and a height of 5.3 meters.

It was previously regarded as an enpun (円墳) circular tumulus, but excavation revealed that it was built in two tiers and is in fact a rokkaku-fun (六角墳), a hexagonal mound. It contains a stone burial chamber of cut tuff stones, orientated to the south. The interior walls and floor are covered with plaster, of a structure similar to that at Takamatsuzuka Kofun and Kitora Kofun. The ceiling is carved into a roof shape, which is also similar to Kitora Kofun, but no murals were found.

Archaeological excavations were carried out in 1977 and 1978. The excavated artifacts include fragments of a lacquered wooden coffin, copper nails, iron nails, gilt bronze coffin ornaments and a gilt bronze sword fitting. Human bones of a man believed to be in his 30s were also found.