But the later excavation and research has revealed that its front square part had been removed and leveled out when Heijo-kyu Palace was constructed, and that the original tumulus had been a keyhole-shaped tomb mound with its front square part facing south, whose total length was 253 meters with its front square part being 164 meters in width and its rear round part being 147 meters in diameter.
しかしその後の発掘調査で前方部が平城宮建設のさいに削平されており、本来は墳丘の全長253メートル前方部の幅164メートル後円部の直径147メートルの前方部を南に向けた前方後円墳であることが判明した。