Emperor Nintoku
During the subsequent Kofun period, most of Japan gradually unified under a single kingdom. The symbol of the growing power of Japan's new leaders was the "kofun" burial mounds they constructed from around 250 CE onwards. Many were of massive scales, such as the Daisenryō Kofun, a 486 m-long keyhole-shaped burial mound that took huge teams of laborers fifteen years to complete. It is commonly accepted that the tomb was built for Emperor Nintoku. The "kofun" were often surrounded by and filled with numerous "haniwa" clay sculptures, often in the shape of warriors and horses.