At the side of the entrance of the park stands Fukuchiyama City Sato Taisei Memorial Art Museum whose structure is of Sumiyagura (turret) Style Castle Architecture.

Perhaps for this reason, the lord got permission from the new Meiji government to convert the jinya into a more solidly-built castle, and built a yagura-mon gate, a tatsumi-yagura turret, and a three-layer turret on Komugi-yama Mountain in two years starting from 1868.

Tenshu was sometimes regarded as the largest Yagura (turret) in a castle and in some castles was called Oyagura (big turret) or Tenshu-Yagura turret.

The castle structures, mainly Tenshu and multiple-tiered Yagura, were, in many cases, constructed with the roofs being piled up in a complicated way, and when story and tier should be identified, the numeration for ordinary housing, simply '-story,' may make the enumerated data improper for knowing the outline of the castle structures.

In castles, a nagaya called the Tamon-yagura (turret) was built on a mound and was used as ordinary residential houses while effectively serving as a point of defense.

They were also built in the Middle Ages together with tradesmen's houses (merchant's houses), and in modern times, with the arrival of firearms, lime plaster stud wall techniques were also used on castles for fire-proofing and bullet-proofing, and mud walls over 30 centimeters thick as Dozo-zukuri style were extensively used on defensive structures such as guard towers and turrets keep from the late Azuchi-Momoyama period to around the Edo period.

A long time ago, a wooden gate was put in the open section and two turrets were built on either side near the gate for emergencies.

"Chusei Jokaku Jiten" (Dictionary of Medieval Castles) states the possibility that a tamon yagura (long guard tower) once stood on the remains of the earthen mound.

Yagura (fortress turret)

Yagura refers to a turret, built in a fortress, as a guard tower or a watchtower.

At the end of the Sengoku period (period of warring states), when modern fortresses started to be built, yaguras were built on the foundation stones, with tiled roofs and thick clayey walls to prevent fire and bullets.

The yaguras that were built in a large fortress of the castles that were deeply related to the bakufu, such as Edo-jo castle, Osaka-jo Castle and Nagoya-jo Castle, had structural features, similar to a tenshu, such as a main building with several rooms.

In the small yagura built in the local fortress, there was one room and no distinction between the main building and an aisle.

For the same purpose, surveillance yagura have been built not only in a fortress but on the streets of Kyoto City, which was portrayed on "Ippen Shonin Eden (Pictorial biography of the monk Ippen)."

Houses, turrets (citadels) and keeps were also included in the construction.

The form of stone walls, castle towers and turrets (citadels) which were main elements of castles at the time, were created when Hisahide MATSUNAGA built Tamonyama-jo Castle and Shigisan-jo Castle after the end of Muromachi period or when Nobunaga ODA built Azuchi-jo Castle.

The castle sites used as garrisons were targeted by the United States Armed Forces during the Pacific War (The Greater East Asia War) and citadel constructions, such as castle towers, turrets and gates of Nagoya-jo Castle, Wakayama-jo Castle and Hiroshima-jo Castle, which were built before the Edo period, were burnt out in air raids or with atomic bombs.

Many gates and turrets of citadels escaped from being damaged in fires and wars and still exist to this day, in contrast to castle towers, with most of them being designated as national important cultural property.

There were cases in which castle towers, turrets, gates, palaces, earthen walls and stone walls were reconstructed or excavated citadels of the medieval and Sengoku periods were reproduced during this period.

Stone walls were used at several important parts of a citadel even in the medieval period, but stone walls reinforced by stacking stones on the surface of earthen walls developed as the need arose to build heavy turrets near the citadel in the Azuchi-momoyama period.