Asakumi Iwaya Kofun

The ground around the mound has been levelled, so the original shape is unknown. At present it has the form of a round mound 20 metres in diameter, but it may originally have been a square mound of about 30 metres on a side.

The chamber is built of large cut stones, and its burial chamber is constructed like a sarcophagus. The total length of the chamber is about 5.4 metres. The burial chamber measures 1.9 metres in length, 3.1 metres in width and 2.1 metres in height; the passage measures 3 metres in length, 1 metre in width and 1.5 metres in height. The chamber has a wide rectangular plan set at right angles to the main axis of the chamber, with the passage joined to the long side. The stone is rhyolitic pumice lapilli tuff (Arashima stone). The rear wall of the burial chamber has small cut stones stacked on top, and the side walls are single slabs. The front wall combines three cut stones, with recesses cut around the entrance of the burial chamber to receive a sealing stone and a threshold stone laid on the floor. The passage is also built of upright cut stones, and its entrance has a sealing stone of slab type, partly surviving.

Because of the rectangular burial chamber plan entered from the long side and an entrance made of several stones, the chamber is placed at an early stage before the type became standardised.

The grave goods inside the chamber are not known in detail. Fragments of Sue ware (the foot of a jar with small jars attached, a jar rim and jar sherds) were collected during the survey of the mound. The construction date is estimated to the 6th century, in the Late Kofun period.