Miyayamazuka Kofun

Miyayamazuka Kofun, also called 椿井宮山塚古墳 and 椿井宮山古墳, is a circular burial mound at 椿井 in 平群町, 奈良県. It was built on the western slope of 矢田丘陵, with the mound top at an elevation of 125.1 meters. It is a designated historic site of 奈良県, and entry into the stone chamber is currently restricted.

The mound is circular or oval, measuring 26 meters east to west, 24 meters north to south, and about 7.1 meters high. Its burial facility is a side-opening horizontal stone chamber facing south. The chamber has a nearly square main room, a domed ceiling, and a very short passage. It was built from flat natural stones and split stones, with the walls rising vertically below and leaning inward above.

The mound was probably constructed in the late to end of the 5th century, during the middle period of the Kofun era. It is among the oldest mounds in 平群谷 and one of the early horizontal stone chambers in the 畿内 region, making it important for studying the development of this burial form. Research included chamber surveys in 1991 and 1992 and a mound survey in 1999. Stonework was loosened by the 兵庫県南部地震 in 1995.

The mound was altered when it was incorporated into the earthwork defenses of 椿井城 during the medieval period. Its name comes from its position beside 春日神社. Monuments of this kind in Japan are known as kofun, or burial mounds, and were built mainly between the middle of the third century and the early seventh century CE. Plain round mounds, as well as keyhole-shaped and other forms, are found among them.

Miyayamazuka 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 "宮山塚古墳", shown in the original language.