Shinmeiyama-kofun Tumulus (神明山古墳)
It was presumed that this huge tumulus was constructed in the latter half of the fourth century and that, with its length of 190 m, was the tomb of the head of a local ruling family concerned with the sea. However, later it was pointed out that, with Lake Takeno in the north-west of the tumulus, the tumulus was beside a lagoon and was separated from the sea by sand dunes. Built in parallel with a coastline and covered with fuki-ishi (a stone covering an old tomb), it shone white and could be viewed clearly from the sea, constituting a sign indicating a port location. After the latter half of the fourth century, large-scale keyhole-shaped tumuli appeared in relation with ports. For examples, in Kazusa Province, Owari Province, Tango Province and Hoki Province, and so on, the largest tumulus in each of these provinces appeared in relation to the sea as well. From these facts, a theory insisting that a Tango kingdom (Tango government) existed has been presented.