kofun are ancient burial mounds found in Japan, dating from the 3rd to the 7th centuries. They are characterized by their keyhole shape and are often surrounded by moats. These mounds served as tombs for powerful individuals, including emperors and elite members of society. The largest kofun, known as the Daisen Kofun, is located in Osaka and measures over 400 meters in length. Many kofun contain grave goods, such as pottery and weapons, which provide insight into the culture and beliefs of the time. These structures are significant for understanding early Japanese history and society.