Nasu Government Office Ruins

A County Government Buried Under a Field Long Mistaken for a Temple

For most of the modern era, the gentle terrace above the confluence of the Naka and Hōki Rivers in Tochigi Prefecture was known to local farmers as Umeso Haijiato, the ruins of a vanished temple. Roof tiles surfaced when ploughs turned the soil, and a low earthen platform held its shape across the centuries. The interpretation seemed natural enough. Then, in 1940, a farmer working that platform turned up a small bronze seal inscribed with private characters. The seal would later be designated a national Important Cultural Property and enter the collection of the Tokyo National Museum. It also did something quieter but more consequential: it set scholars to looking at the site again.

Excavations beginning in 1955 and intensifying from 1967 onward, when a regional land-improvement project forced systematic survey, revealed something quite unlike a temple. Underneath the field lay the rectangular bones of a Nara- and Heian-period county office, with more than thirty building footprints arranged in deliberate blocks. The site was redesignated as Nasu Kanga, the seat of Nasu District government, and in 1976 it received protection as a national Historic Site. What had been read for decades as a religious ruin turned out to be the administrative center of an entire province-tier county, operating from the late seventh century into the early tenth.

Reading the Layout: Four Blocks, One Bureaucracy

The site occupies a tableland roughly 200 meters north-south by 400 to 600 meters east-west, divided by drainage ditches into four functional quarters. The western block, enclosed by a substantial ditch four meters wide and one meter deep, is interpreted as the granary precinct, the sōin. Here archaeologists recovered the post holes of multiple buildings raised on the sō-bashira pattern, where pillars stand at every column intersection, a structural form chosen specifically to bear the weight of stored rice and tax goods.

The eastern block tells a different story. Its post holes line up in the side-pillar pattern typical of working offices rather than storehouses, and from this archaeologists infer the gunchō, the assembly hall where county officials conducted business. Fragments of inkstones and pottery sherds bearing ink-written characters surfaced in this part of the site, leaving little doubt that documents were drafted, sealed, and filed here. The central block remained partly under modern housing during excavation but produced two stone-based buildings also identified as warehouses. The southeastern block, with its dense scatter of post holes and at least one hexagonal structure that is exceptionally rare in Japanese archaeology, appears to have housed the tachi residential quarters or perhaps a kuriya kitchen serving them.

At the heart of the complex once stood a tile-roofed building set on dressed stones. When first uncovered, its red-painted timbers and formal foundation prompted excavators to call it the main hall. Continued digging shifted that reading: the structure is now understood as a shōsō, the principal granary, surrounded by satellite storehouses in a planned arrangement. Sometime in the tenth century the tile roof collapsed, and a smaller post-and-beam building of five by two bays was raised on the same platform, evidence of how the office continued to function after its grandest phase had ended.

Why a County Office Belonged Here

Placement was no accident. The Nasu region in what is now northeastern Tochigi sits along the old Tōsandō, the eastern mountain highway that linked the Yamato capital to the provinces beyond the Kantō plain. Excavators have traced a roadway extending north from the Nasu Kanga site, almost certainly a spur of the Tōsandō, and on its northward alignment lies the ruined Jōhōji temple site. The administrative complex was positioned to control traffic along the highway, manage tribute flowing south from the frontier, and oversee the agricultural land of the Hōki River basin.

The deeper reason runs through the surrounding landscape. Within a few kilometers stand the Samurai-zuka tumuli, designated a national Historic Site in 1951, which mark this district as a center of power long before the imperial bureaucracy arrived. Four kilometers north, at Kasaishi Shrine, stands the Nasu Kuninomiyatsuko monument, designated a National Treasure in 1952. Inscribed in 700 with seven hundred characters of formal Chinese, the stele commemorates the death of a local chieftain and is one of the three great surviving early Japanese inscriptions. When the central government drew up Nasu District under the ritsuryō codes, it placed the new county office in a region with deep memory of its own authority, a deliberate alignment of new institutions with old prestige.

What a Visit Reveals

The site today is preserved as a historic park, open without admission to anyone who wishes to walk it. Foundation stones marking the central shōsō remain visible on their low platform, and explanatory panels installed by the Nakagawa Town Board of Education trace the building outlines across the grass. The terrain still reads as it would have to a Nara-period clerk approaching from the south: the land rises gently, the river bends below, and the surviving stones suggest the dimensions of the structures that once stood here.

The richest interpretation lies a short distance away at the Nakagawa Town Nasu Fudoki no Oka Museum, which holds the roof tiles, inkstone fragments, and ink-inscribed pottery recovered from the excavations, alongside a reconstructed scale model of the central granary. The museum tells the broader story of Nasu from the Jōmon period through Heian, with the county office as one chapter in a five-thousand-year sequence of settlement. The bronze seal that began this whole reinterpretation is held by the Tokyo National Museum and occasionally appears in their archaeology galleries, four hours south by train but worth the journey for anyone tracing the find that rewrote the site's identity.