Maruoka Castle Tower

Maruoka Castle Keep

The roof of Maruoka Castle's keep is laid not in fired clay but in stone. Thin slabs of blue-green Shakudani tuff, quarried from the volcanic hills near Fukui City, cover the two roof tiers, and their combined weight is estimated at somewhere between 75 and 120 tonnes pressing down on the timber frame below. It is the only surviving castle keep in Japan roofed this way, a solution to a local problem: ordinary ceramic tiles crack and shed water when they freeze, and the Hokuriku coast spends much of each winter under heavy snow.

The keep stands on a low, isolated hill in Maruoka, now part of Sakai City in northern Fukui Prefecture. It is a compact structure, two roofed tiers enclosing three interior floors, built as an independent watchtower-type keep: a square base story carrying a smaller lookout above. Of the dozen original castle keeps that survive in Japan, this is the only one in the Hokuriku region facing the Sea of Japan.

An Important Cultural Property With a Contested Birthday

Maruoka Castle was founded in 1576, when Shibata Katsutoyo, a nephew of the warlord Shibata Katsuie, raised it as a subsidiary fortress of nearby Kitanosho Castle. For a long time the keep itself was assumed to date from that founding, and the building's archaic features supported the idea. The stone base is built in nozura-zumi, a rough technique using unworked field stones, and the eaves are left bare rather than plastered over, both hallmarks of early castle construction. On that reasoning Maruoka was often promoted as the oldest surviving keep in the country.

Science complicated the story. Between 2015 and 2019 a research committee commissioned by Sakai City examined the keep's timbers using tree-ring dating, radiocarbon analysis, and oxygen-isotope measurement. Most of the structural members turned out to have been felled in the late 1620s. The committee concluded that the keep as it stands was built during the Kanei era, around 1628, under Honda Narishige, the first lord of the newly independent Maruoka domain. The national database administered by the Agency for Cultural Affairs still records the building under the 1576 founding date, so visitors will see both figures cited; the discrepancy reflects the difference between when the castle was established and when this particular tower was raised.

The redating cost Maruoka its claim to be the oldest keep, but it did not touch the building's legal standing. Maruoka Castle Keep was designated an Important Cultural Property on 30 January 1934, and it remains one. Earlier research had also found traces of wooden shingles beneath the stone tiles, a hint that the present stone roof may not have been the original covering.

What to Look For on a Visit

The climb inside is steep. The staircases between floors are closer to fixed ladders than to stairs, pitched at angles that ask visitors to use the rope handrails, and the experience of hauling yourself up through the dim interior is part of what makes the keep feel genuinely old. From the top floor, windows on all four sides open onto the Fukui plain and, in clear weather, the mountains beyond.

Outside, the stone roof rewards a slow look. The slabs sit heavier and flatter than clay tiles, giving the building a grey, weathered solidity, and the same Shakudani stone appears in details around the structure. The keep survived a major test in 1948, when the Fukui earthquake brought it down. Rather than rebuild from scratch, workers salvaged the original beams, pillars, and stones and reassembled the tower from its own fallen pieces, completing the work in the mid-1950s. The building you climb today is substantially the same timber that stood before the quake.

One practical note: a multi-year conservation project running from 2025 to 2027 is carrying out seismic strengthening and roof repairs. Scaffolding and protective sheeting cover the keep during parts of this period, and access to the interior and to areas of the main bailey may be restricted depending on the stage of work. Anyone planning a trip specifically to climb the keep should check current conditions with Sakai City before setting out.