This tumulus (ancient grave mound) is in the shape of two quadrangles and was built at the beginning of the 5th century. The tumulus itself is 66 meters long. The fore quadrangle is 18 meters wide and 1.5 meters high; the aft quadrangle is 36 meters long on one side and 4.5 meters high. The rectangular area around the tumulus thought to be a moat surrounding the clay around a stone pit where the coffin was laid. This tumulus was recognised as a national historical landmark in 1974. The Ohsumi Minamizuka Tumulus to the West is the same size and shape. They are a rare example of two of these double-quadrangle tumuli (zenpoukouhoufun) side by side.