The Kofun period marks the earliest era of recorded history in Japan, named after the massive burial mounds (kofun) built for the ruling elite. These mounds often take a unique 'keyhole' shape, with a circular mound at the back and a trapezoidal mound at the front. The largest of these, the Daisen Kofun (attributed to Emperor Nintoku), is over 480 meters long and surrounded by three moats, making it one of the largest tombs in the world by surface area. Buried within these mounds were precious goods like bronze mirrors, iron swords, and 'Haniwa'—clay figures of warriors, horses, and houses placed on top of the mounds to protect the deceased and define the sacred space. The construction of these massive monuments indicates a highly organized, centralized state emerging in Japan during this time, with the ability to mobilize vast amounts of labor.