noun
A mound of earth over a grave; literally 'earth bun' from its rounded shape.
古墳時代の土饅頭がこの地域に点在している。
Burial mounds from the Kofun period are scattered around this area.
古墳 is the formal term for ancient burial mounds, while 土饅頭 is a more colloquial, descriptive word.
Compound of 土 (earth) and 饅頭 (steamed bun), from the resemblance of the rounded mound to a bun.