Charm of the Oka Castle

wall Stone wall

Never Beaten Impregnable Castle: From the castle of the earth to the castle of stones

The Oka Castle which has been famous for the never beaten strong castle. The reason of it can be said with “a sheer cliff” and “the group of stone walls”, which was built on the cliff.
In the end of the Warring States period, in Tensho 14 (1586) to the Oka Castle protected by Chikatsugu Shiga, the large army of the Shimazu clan of Satsuma (Kagoshima) made an attack on it, however they could not capture the tall and steep Oka Castle, and the history of their retreat remains. The Oka Castle in those days, there weren’t the group of stone walls, it was the mountain castle built with the earth such as earthen wall and the dry moats.
In Bunroku 6(1594), Hideshige Nakagawa who became the load of Oka Castle did a large repair to change from “The castle of the earth” to “The castle of all rocks” that was shown in getting rid of the Shimazu Clan.

The breathtaking stone walls: The huge castle walls of rocks

The beginning of early modern times, the Oka Castle repaired to the castle of all stone walls surrounds the top of sheer cliffs, and became the giant castle with walls and watch towers lined up on them.
After the becoming ruined castle in the Meiji period, because the buildings of the inside of the castle were pulled down, only the stone walls are remained. However, each sections of the castle, the traces of gates, and the watch towers were all built with the rock walls, with the very impressive stones walls, we can guess the figure of the huge castle. Especially, the high stone walls constructed on each cliff from the north of Sannomaru (third keep) to Ninomaru (second keep) generate the magnificence and beauty, so they are the must see.
Trivia “The stone walls like byobu or the folding screens”
The high rock walls at the Sannomaru (third keep), looks like the shape of a folding screen. Because of this, it was possible to shoot arrows from the two directions. That’s way it was helpful to repel the enemy force.
The beauty of the stone walls just like the old castles in Europe
The Otemon, at the main entrance of the Oka Castle, we can see the stone walls just looking like old castles in Europe. Also, there is a stone wall with the rocks piled up in the shape of the arch, and we can guess how particular about the beauty Nakagawa clan was.
Strange looking "kamaboko stone"
At Otemichi being used, the main entrance, there are mysterious arch shaped stone walls. It looks like kamaboko(=fish cake) so it is commonly called "kamaboko stone".
There are many parts unknown in the skills of its production too, and it is one of the characteristics of Oka Castle which can’ be found in other castles.
Trivia “The welded tuff of Mt. Aso “
The stone walls of Oka Castle were built using the welded tuff of Mt. Aso. The pyroclastic flow that flowed into the river due to the eruption of Mt. Aso was cooled and turned into stones. These stones were easy in processing, and suited for the production of the stone walls.
Still now, we can observe the traces of stones cut off in the river of castle town.

The stone walls used a lot of various techniques.

So many techniques and the ways of stacking up are used for the stone walls of Oka Castle. Let us present how to process and stack stones that we can see inside the castle.

・The classification depending on the degree of stone processing

Nozurazumi (piling up the natural stones)
The techniques without using too many ways in the processing on the natural stones.
Kirikomihagi (shaping into a square)
The way of the techniques in shaping rocks, and getting rid of the openings by sticking firmly.
Uchikomihagi (shaping the stocked stones)
The techniques decreasing openings processing a little on the side of joint or between stones.
Among these techniques, “kirikomihagi” and “uchikomihagi” can be seen a lot in the Oka Castle. Particularly, at the drum watch tower, huge stones in the size of two meters are all piled up without empty space by “kirikomihagi”, and we can see that the Oka domain had the high level techniques for the loading stones.

・The classification depending on the ways of loading stones.

Ranzumi (loading irregularly)
The stone walls irregularly piled up.
Nunozumi (lying together in rows)
The rocks piled up making them looking like on the straight line.
Tanizumi (stacking diagonally)
The stone walls made by dropping down the stones diagonally.
Sangizumi (piling the stone sticks at the corners)
The way of piling up the stones at the corners of the stone walls.
In the Oka castle, “nunozumi” and “tanizumi” are often used, and at the corners of stone walls, “sangizumi” is also used often.
Trivia “ Kagamiishi” (the large stone)
In those days, the style of embedding especially the large stones into the stone walls were seen at each castle in order to show off the skills of craftsmen and the power of daimyo to the outside.These large stones are called “Kagamiishi” At Oka Castle, they can be seen at Otemon (main entrance). Please do try to find them.
Trivia “The stones having the carved seals ”
Besides, “kagamiishi”, there are “the stones having the carved seals” as a characteristic at each castle. At Oka Castle, they can be seen at the stone walls of Honmaru (the keep). Please do try to find them.