Yanagi Government Office is late Heian period ruin of the building complex which belonged to the Oshu Fujiwara clan. The cmplex was called "Hiraizumi no Tachi." It appeared in a period historical record and was used for the family's official ceremonies or political affairs. Features of the buildings and moats were excavated along with various bistorically significant artifacts that proved active relations between this area and Kyoto or even to places over seas during that time. It is particularly important among the cultural heritage of the Hiraizumi area because the ruins were the center of the political and administrative activities of northern Japan at that time.
(reference: official board on the site)