location Mozuume-machi 1, Kita-ku
Located approximately 500 meters north of Nisanzai Kofun, Jonoyama Kofun has become a kofun park called Jonoyama park. At first glance, it appears to be nothing more than a mound of earth. But until 1955 or so, ribs of rice fields have indicated the outline of the existed moat.
Originally, it was a scallop shell-shaped burial mound,facing west. However, due to the Land Division Reorganization Project in 1968, its shape was drastically altered, and the site was left as a park.
The mound was 69 meters long, with the round part about 55.6 meters in diameter and 7 meters high and the square part 30.7 meters wide. The existence of fukiishi and a row of haniwa has been confirmed.
When the front square part was removed and flattened, a mass of clay was found in the center of the mound. There is a possibility that it might have been a part of its burial facility.
Originally, the burial mound's front square portion faced west and the mound was scallop-shaped; however, due to a Land Division Reorganization Project in 1968, the mound's shape changed drastically. Later, based on the results of the excavation, it was restored and preserved as a park.
The mound's overall length is 69 meters and the diameter of the rear circular portion is 55.6 meters. It stands 7 meters high and the front square portion has a width of 30.7 meters. The existence of stone buttresses and clay figures has been confirmed.
When the front square portion of the mound was being stripped away, a mass of clay was found in the center of the burial mound.
It is said that this might possibly have been the burial chamber.