The Osaka Castle Tenshukaku is one of Japan’s most famous historical structures, standing tall in the center of Osaka Castle. Its majestic appearance is a familiar symbol of Osaka and attracts many tourists.
However, the castle tower, considered a masterpiece of castle architecture, has left behind many mysteries and unknown history throughout its long history. In this article, we will introduce some of the major mysteries and history surrounding the Osaka Castle Keep.
Mystery #1: Who designed and supervised the Osaka Castle Keep?
When Toyotomi Hideyoshi built Osaka Castle in 1583, there is still no established theory as to who designed and supervised its construction.
Later in 1615, Osaka Castle fell during the Osaka Summer Campaign, and the Osaka Castle Keep also collapsed.
In 1628, under the order of the Tokugawa Shogunate, reconstruction of Osaka Castle was begun by Tokugawa Mitsunao.
The reconstruction was designed and built by Masakiyo Nakai and Shigenari Kagai, two carpenters under the orders of the Tokugawa Shogunate. The interior structure of the current castle tower bears some resemblance to the tower depicted in the “Fushimi Castle” painted in 1603. However, Fushimi Castle was destroyed by fire in 1602, and its exact interior structure cannot be determined.
These mysteries point to the possibility that the present keep was not simply rebuilt, but was newly designed and constructed by Masakiyo Nakai and Shigenari Kagai, two carpenters under the shogunate’s authority, incorporating elements of past keep structures. However, there are no blueprints of the reconstruction made by the two carpenters.
Mystery #2: Where are the plans for the Osaka Castle Keep?
The wooden parts of the keep were assembled using traditional Japanese architectural woodwork. Masakiyo Nakai and Shigenari Kagai, who were responsible for the reconstruction, were craftsmen with advanced knowledge of traditional Japanese wooden construction techniques, and it is said that they were highly skilled in assembling the complex wooden structure without blueprints.
Structural innovations such as the placement of columns and beams, and the installation of braces, made possible the outstanding earthquake resistance of the Osaka Castle tower. The aesthetic sense of traditional Japanese wooden architecture was also well developed, resulting not only in strength and earthquake resistance, but also in an elegant appearance.
The castle tower uses the traditional cypress bark thatching technique. However, there is a mystery to this hiwara thatching. The quality of the cypress bark is not uniform, and materials from various regions are used in different ways. In addition, although hiwadabuki roofing is generally considered to be less durable, the Osaka Castle tower has achieved a durability of almost no roof repairs over a long period of approximately 400 years. Why is this?
In fact, the hinoki bark thatch on the Osaka Castle tower is made from a variety of materials from different regions, and different qualities of hinoki bark are used by different craftsmen to increase the durability of the roof.
For the steeper slopes of the roof, hinoki bark from Miyazaki Prefecture is used because of its high strength. The hinoki bark from Miyazaki Prefecture is characterized by its long fibers and high strength.
For sunny areas, we use highly durable hinoki bark from Nagano Prefecture. Nagano hinoki bark is characterized by its high oil content and durability.
For the surface of the roof, we use hinoki bark produced in Gifu Prefecture, which is aesthetically pleasing. The hinoki bark produced in Gifu Prefecture is characterized by its less uneven coloring and superior aesthetics.
The use of different types of hinoki bark in the hinoki bark roofing of Osaka Castle Tenshukaku is based on the quality of the hinoki bark. Masakiyo Nakai and Shigenari Kagai, who were responsible for the reconstruction, were well aware of the differences in the quality of the hiwadabuki bark.
Mystery 3: What is the three-dimensional trick?
It has been pointed out that the Osaka Castle tower may be a three-dimensional trick in which the size and shape of the tower changes depending on the viewpoint.
For example, the height of the lower stone wall looks low when viewed from above, but in fact it is over 20 meters high in some places. Also, the beautiful curved patterns of the stonewalls appear to be disconnected when viewed from afar, but they are connected when viewed up close. Thus, Osaka Castle may be the site of various three-dimensional tricks.
The following are the main three-dimensional tricks that have been pointed out.
The illusion of the difference in height of the stone walls
The stonewalls surrounding the castle tower seem to be very high when seen from below, but look low when seen from above. This is thought to be due to the intentional difference in height of the stonewalls, which creates the illusion of perspective.
The difference in the connection of the stone wall patterns
Stone wall patterns drawn with beautiful curves appear to be disconnected when seen from a distance, but they are firmly connected when seen up close. This difference seems to have been created by skillfully manipulating the curves of the pattern and the size of the stones.
Illusion of the size of the windows of the castle tower
The windows of the castle tower appear to be small when seen up close and large when seen from afar. Moreover, the shape of the windows also appears to be distorted when the viewpoint is changed. This illusion is believed to be created by devising the position and shape of the windows.
There are several hypotheses as to the intention of these three-dimensional tricks, such as whether they were required for defense, merely decorative, or had some cryptic meaning, but it is not certain. It can be said that they are the result of the advanced wisdom and technical skills of the stonemasons who were assembled from all over Japan for the construction of the tower.
It can be said that the charm of the Osaka Castle tower was born from the historic skills of the craftsmen of the time.
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