The Great Keep
First Floor
(1) Walls and Weatherboard
On the exterior of the keep, the upper portions of the white plaster walls have been left exposed, while the lower parts are covered by black-lacquered weatherboard. Plaster walls degrade relatively quickly when left exposed to rain and snow, and the weight of the structure above increased the risk of collapse. The siding was added to protect the parts of the wall that were outside the coverage of the roof eaves and exposed to the elements.
The photograph on the right shows a portion of the second-floor wall that was removed during repairs in the 1950s. The earthen walls beneath the white plaster were made by wrapping a wooden lattice frame in rope and coating the frame in layers of mud. At roughly 29 centimeters thick, the walls on the first and second floors would have been impenetrable to musket fire. The higher floors, which would only have been hit at an angle, have slightly thinner walls.
The additional thinner layer of wall that can be seen in the photograph was added as part of earlier repairs that were completed in 1913.
(2) Ishi Otoshi
The openings in the floor that protrude over the stone-wall foundation are defensive features called ishi otoshi. These openings allowed defenders to attack enemies who attempted to scale the castle walls. The term ishi otoshi literally means “stone-dropping,” but the openings were more likely used to provide additional lines of sight for gunners defending the castle.
There are 11 ishi otoshi built into the first floors of the Great Keep, the Inui Keep, and the Roofed Passage. The openings are placed at the corners and midpoint of each wall to provide vantage points over the foundation below.
(3) Foundation and Corridors
The center section of the floor is approximately 50 centimeters higher than the surrounding corridors. This design was necessary to accommodate the double-layered structure of wooden beams that make up the foundation, which can be seen through the gaps.
Items on Display
Various objects removed from the castle during repairs in the 1950s are displayed along the corridors of the first floor.
Section of the Keep Wall
This portion of earthen wall was removed from the second floor of the Great Keep during repairs in the 1950s. It is approximately 29 centimeters thick. The wall was made by applying layers of mud plaster to a wooden frame that had been wrapped in rope, then adding a layer of white plaster as a final coat.
Shachi Roof Tiles
Shachi are legendary creatures with the heads of tigers and the bodies of fish. Tiles shaped like shachi were placed on the roofs of castles because it was believed they would protect the buildings from fire. These shachi tiles once adorned the roof of the Great Keep. The open-mouthed male shachi was placed on the southern edge of the ridge, while the close-mouthed female was placed on the northern end.
Support Posts for Shachi Roof Tiles
These posts helped anchor the shachi tiles to the roof of the keep. The decorative tiles would have covered nearly 80 centimeters of the 190-centimeter posts. Ink inscriptions on the posts indicate that they date to 1843.
Foundation Support Post
This post was one of 16 that made up the underground support structure of the foundation. The foundation was excavated during repairs in the 1950s, and it was found that every post had rotted but one. By the turn of the twentieth century, the Great Keep had begun to tilt, likely because the rotted foundation could no longer support its thousand-ton weight.
Gegyo Bargeboard Pendants
Wooden ornaments like these commonly adorn the gables of castles. The decorations, which were introduced from China, were originally shaped like fish and were thought to help protect a building from fire, which was an ever-present threat to the all-wooden construction of traditional buildings. The central element of this gegyo is shaped like a turnip, which was a popular design in Japan during the Edo period (1603–1867).
