Castles in Japan underwent their most intensive phase of development in the Sengoku (Warring States) era from the 15th to the 16th century.

The castles were built with the object of keeping the enemy out. They are elaborate in design and strongly fortified. Their magnificent architecture also served to demonstrate the power of the lord of the castle.
If you are fortune to visit Japanese castle, you can enjoy the beauty of the castle exterior designs, but do not miss the opportunity to look at the cleaver defense designs hidden inside for more fun. The Hiroshima Castle also has many defense secrets.
Castle Towers protected by courts, moats and rivers

The tenshu (castle tower) was usually protected in order by fortified courts called honmaru, noinomaru and sannomaru meaning “main court”, “second court” and “third court” respectively.
The courts were surrounded by a few moats (e.g., inner, middle and outer moats), and natural rivers to isolate the castles from the outside.

In the Hiroshima Castle, the north moat modified from a natural river and middle and outer moats shown in the castle map have already been filled up and the sannomaru can no longer be seen due to the past city development.
Photo source:
http://www.pcf.city.hiroshima.jp/virtual/VirtualMuseum_j/exhibit/exh1207/exh120700.html
However, both the honmaru and the ninomaru still remain and are open to the public.
The watchtowers and the main gate were restored

Turrets, watchtowers, were constructed along the moats and connected by long walls for defense. The Hiroshima Castle used to have 88 turrets which have all gone away.
A few buildings were restored in the ninomaru by the original construction method and you can enter the buildings to feel the Samurai era.
The Masugata stops the enemy flow

In the entrance of the courts, the masugata, a square embattlement which forced anyone entering the castle to make a turn before he could pass through the next gate, was constructed. It could not only cut the enemy flow but also allow to shoot the enemy from 360-degree directions in a battle.
You can see the masugata at both the honmaru and the ninomaru in the Hiroshima Castle.
Photo source: https://wako226.exblog.jp/15790031/
Shachihoko prevents fire

The topmost roof of the castle tower is decorated with a pair of gilt dolphin-like fish with tiger’s heads, called shachihoko. These were thoughts to have the power of preventing fire.
Interestingly, they are a pair of the male and female animals with some different appearances. For example: the direction of nose holes, the design of their scales. You can check out the differences on the real shachihoko pair displayed inside the Hiroshima Castle which now serves as History and Culture Museum.
Photo source: https://ja.wikipedia.org/wiki/%E9%87%91%E9%AF%B1
The beautiful castle tower was the final retreat in battles
The tenshu was the stronghold and headquarters of the castle, and the place of final retreat in a battle. This was where the lord of the castle would live when the castle was in a siege, while the honmaru was the lord’s residence to stay in peace.

The Hiroshima Castle used to have three tenshu, one large accompanied by two small tenshu. The three-connected tenshu figure would look so beautiful and well demonstrate the power of the lord at that time.
Photo source: http://8787pc.com/%E4%B8%AD%E3%83%BB%E5%9B%9B%E5%9B%BD%E3%81%AE%E5%9F%8E.html
The small tenshu were torn down when Samurai era ended, and the large tenshu was destroyed by the atomic bomb. The large one was reconstructed 60 years ago with the same exterior design.

Please come visit to enjoy the beauty of the Hiroshima Castle tower surrounded by Sakura, cherry blossom, in spring and beautiful greenery in summer.
Zigzag walls pierced by loopholes
Various devices were used to make the castle more secure against attackers.

The castle tower and watchtowers were provided with loopholes called sama through which guns could be fired or arrows could be shot.
The loopholes are circles, squares or triangles for guns and rectangular for arrows.
Photo source: https://tyanbara.org/sengoku-history/201812088220/

The zigzag wall designs allowed to shoot all attackers from the side by eliminating the dead angles, while the plane wall had some restriction in the shooting angle.
Photo source:
http://north-alps.la.coocan.jp/image/matsumotocastle/gakusyukai/05yokoya/yokoya.html
Rocks fall on Ninjya’s heads

The special chambers called ishiotoshi were built out over the stone wall of the castle. Its floor could be opened downwards to drop rocks onto the heads of Ninjya trying to scale the stone walls.
You can see the ishiotoshi inside the Hiroshima Castle tower where Samurai armor gears are also displayed. You can try on some of the armor gears free for photo shooting.
Photo source: https://tyanbara.org/sengoku-history/201812088220/
Time trip to 400 years ago by the stone wall watching
You cannot miss the chance of stone wall watching especially in the Hiroshima Castle. The stone wall construction skills dramatically developed around 1600.

It happens to be coincident with the timing when the 1st and 2nd lords of the Hiroshima Castle were forced to leave the castle in such short periods, 9 and 19 years respectively.
By carefully watching the stone wall construction methods, you can notice the affairs occurred about 400 years ago. This is a long story, and will be explained in our tour.

Of course, you can enjoy the city views from the top floor of the tenshu just like the lords of the castle did hundreds of years ago.
Enjoy Hiroshima castles!