It is a 106-meter-long zenpo-koen-fun that is a mound shaped like a keyhole. This tumulus is the largest in Tokyo and is said to have been built in the 5th century.
Shiba Maruyama Kofun is a tumulus that is a 106-meter-long zenpo-koen-fun (a keyhole-shaped mound). It is said to be the largest tumulus in Tokyo with the circular part at 64 meters in diameter, the square part at 40 meters in width at the front, and the narrowest part between the circular and square parts at 22 meters. It is located on the hill at a height of 16 meters above sea level with its frontal part facing south-southwest. Its original shape has been significantly damaged; particularly, the top and the back circular parts have been scraped off. When Japanese archeologists investigated the tumulus in 1898, the main part (the burial facility), thought to have been at the center of the back circular part, was already lost. The corpse and its accompanying burial goods were also missing. From the shape of the frontal part, which is lower and narrower, as well as the condition of the site, it is estimated to have been built in the 5th century. It was designated as an Important Historical Property of Tokyo in 1979. It is within walking distance from both the Toei Subway Mita Line Shiba-koen Station and the JR (Japan Railways) Yamanote Line Hamamatsucho Station.