Gigantic stones are used for the stone wall around the entrance to Honmaru (main enclosure and keep) to present a dignified and powerful castle lord. The largest one is a standing thin flat stone that is 4.1 meters in height and 3.4 meters in width. According to excavation research, Kagami Ishi is believed to have been built around the time when the Ikeda Clan became the castle lord.

 The three-tiered four-story turret was the largest turret in the castle, and it served as an important point in protecting the main entrance to Honmaru. According to tradition, it is said that this Onando Yagura was moved from Kameyama Castle (Numa Castle) which had been maintained by Ukita Naoie. The walls were covered with black clapboards, and documents and tools used for the administration of the domain were stored here.

 “Kurogane” means iron. It is said that the name of the gate comes from the fact that its wooden part was completely covered with iron plates, presenting a stern and solemn impression. It was a turret gate leading from the south side of the lower level of Honmaru to Omote Shoin (buildings for administration) in the middle level of Honmaru.

 A solid cliff face of bedrock at the edge of a hill called Okayama supports the stone walls of Okayama Castle. Here, a huge bedrock is exposed, and it can be observed that natural stones are piled up following the shape of the bedrock, forming a corner part at obtuse angles.

 This is a building where attendants of domain retainers who visited Okayama Castle would wait until their masters finished their business. It has been restored and can be currently used as a resting space.

 This stone wall was built by Ukita Hideie by 1597, using unprocessed natural stones. The corner parts sit on high bedrock, but the west side of the stone wall is buried nearly 3 meters underground. Since the stone wall was originally 15.6 meters in height, it is one of the tallest stone walls in Japan leading up to the Battle of Sekigahara.

 At the corner part of the stone wall built by Ukita Hideie, you can observe the traces of the extension of the stone wall where Kobayakawa Hideaki added stones and repaired the stone wall in a straight line. While Hideie piled up large, highly stable stones (at the left side), Hideaki piled up rounded stones.

 This is a gate that leads to the Asahi River behind the castle. “Gangi” means stairs, and the name of the gate is said to derive from the fact that there were originally 61 steps. At the bottom of the stone steps, there was a turret gate to further fortify the castle.

 The foundation for the Tenshu (castle tower) is a stone wall that stands 14.9 meters in height and was built by Ukita Hideie by 1597. This stone wall was built using natural stones and features a flat surface in a scalene pentagonal shape. The site is located at the edge of the hill called Okayama, and the stone wall is supported by its solid cliff face.

 The stone wall under the salt warehouse was built between 1688 and 1703 during the Edo era in order to reinforce the original high stone wall that had been pushed out. The feature of this stone wall is that carefully treated stones with nearly flat surfaces are piled up horizontally and the corners of the uppermost stones are rounded.

 On some of the stones used for the stone wall, you can see openings to insert the wedge to cut stones and engraved marks such as “a mark consisting of a circle and a cross” and “L.” These engraved marks are said to have served as a signature of stone masons, indicating that multiple groups were involved in the stone masonry work.

 This is a turret gate located at the back of Honmaru. Here, there was a compartment within the gate for intercepting the enemy. The compartment was also used as a corridor for the exclusive use of the castle lord, connecting the upper level (the castle lord's residence) and the middle level (buildings for administration) of Honmaru, and the gate was called Roka Mon (corridor gate). It was rebuilt in 1966.

 This is a stone wall from the time when Ukita Hideie built Okayama Castle, discovered during excavation research. When the castle was renovated at the beginning of the Edo era, this stone wall was buried underground at the “middle level” and was expanded extensively to the north.

 This stone wall is about 400 years old and features little processed natural stones, unlike the current stone wall on the north side of the middle level, which was piled up about 30 years later using stones split with a new technique.

 This spot is open to visitors so that they can have a close look at the stone wall and experience the actual development of the castle construction over time.

 This turret was built in the 1620s by Ikeda Tadakatsu to protect the back and northwest direction of Honmaru and the structure remains as it was and is designated as a national important cultural property. The turret is a two-story structure when viewed from outside of the castle, but when viewed from inside of the castle, it is a three-story structure provided with an earthen storehouse with the outer walls made of mud and finished with plaster at the lowest floor.

 On the outside of the castle, the turret is equipped with bay windows that are covered with iron plates and have openings to drop stones at the lower part which served to monitor and intercept the enemy, reinforcing defensive strength. On the inside of the castle, the uppermost floor has a veranda and handrails, and the ceiling is covered with boards, giving it a stately appearance as the name “Tsukimi Yagura” suggests. It can be said that the turret has both peaceful and warlike features that reflect trends at the end of the Warring States period.

 At the top of the north and west stone walls leading to the turret, there are stones provided with openings to shoot at the enemy from inside, which reinforced protection of the castle in combination with the turret.

 This is a large castle gate that fortified the entrance to the upper level of Honmaru. On the upper level, there was Goten (similar to the inner palace of Edo Castle) where the domain head lived, and only a limited number of people were allowed to enter. Therefore, the gate was usually closed, and this is why the gate is called Akazu No Mon (unopened gate). It is said that during the Edo era, the domain head moved through the connecting corridor located near the Tenshu.

 The gate was torn down during the Meiji era, but the exterior was reconstructed in 1966.