Mitani Ishifune Kofun

Mitani Ishifune Kofun is a large burial mound in Mitanimachi, Takamatsu, Kagawa, Japan. It stands on a ridge in the southern part of the Takamatsu plain, south of the city centre, with a reservoir called 石舟池 immediately to its north. It was designated a Takamatsu City designated historic site in 2014 (平成26年).

The mound has a keyhole-shaped plan known as 前方後円墳, with a rectangular front section pointing southwest. The rear circular section is built in two stages and the front section in one. The mound is 88 metres long, with a total length of 101 metres when the surrounding shield-shaped platform is included. It is the largest in the Takamatsu plain, the fourth largest of all kofun in Kagawa, and the third largest 前方後円墳 in the prefecture.

A hollowed-out boat-shaped stone coffin, the type after which the mound is named, is exposed at the centre of the rear circular section. Its details are not known, but it is known to have been set inside a facility within the mound. The stone came from 鷲ノ山 in Kokubunji-machi, and the coffin measures 3 metres long and 0.76 metres wide. A stone pillow forms the head end inside, and a rope-lifting projection is formed at the foot outside.

Judging from the coffin type, construction is estimated to have begun in the early middle period of the Kofun era, placing the mound between 250 CE and 650 CE. Monuments of this kind in Japan are the great burial mounds built mainly between the middle of the third century and the early seventh century CE, a period that takes its name from them. The most distinctive form is the keyhole-shaped mound, seen from above with one square end and one round end.

Mitani Ishifune Kofun is a megalithic mound (tumulus with integral stones) in Japan. A typological estimate: 250 CE to 650 CE. No English Wikipedia article exists for it; the full text below is the Japanese article "三谷石舟古墳", shown in the original language.