This site was designated as a National Historic Site on March 1, 1971, because the remains were excellently preserved and an octagonal tower that has been rarely discovered in this country was recognized to have existed, and they are valuable remains of a temple in terms of architectural history.
遺存状況が極めて良く、国内では発見例の極めて少ない八角塔が検出され、建築史上重要な寺院跡として、1971年（昭和46年）3月1日に史跡に指定された。