This nagaya-mon gate served as the main entrance to the Prefectural Office. In Kobe Ranko, a pictorial history book published in the Meiji period, there is an extant picture of this nagaya-mon gate and an earthen wall stretching to the east. The picture also shows that the gate had a tiled roof and white-painted shitami itabari timber siding. For the reconstruction, the exterior of the nagaya-mon gate was based on this picture. A single gatekeeper, one of the ashigaru servants, guarded the gate when the building functioned as the Administrative Office.