The six stones on display were used in the construction of the main gate of the Kubota castle during the Edo era. Originally there were two pits between stones ① and ⑤, and ④ and ⑥ in the ground.
The existence of the six stones and two pits made it clear that this used to be the main gate area, which was 9.] meters long and 4.8 metres wide, which are respectively calculated from the total distance of 2.1 + 4.9 + 2.1 and 2.4 + 2.4. (See diagram)
It is recognized that all the foundation stones have a mortise and a smooth upper surface. For the stones ② and ③ for Kagami-bashira, these formed the main pillars that supported the doors for the main gate. They are bigger than the others and the mortises of these stones are larger. The stones ① and ④ for Hikae-bachira are the pillars that prevent Kagami-bashira from falling down. They have a 2cm deeper mortise to receive the tenon of the propped pillar on the stone ramparts.
Furthermore, the remains of smaller gates have been found during the process of evacuation, and the city of Akita has preserved them.
(NOTICE) Originally, the foundation stones had been installed where the main gate was rebuilt. To be observed, the stones have been moved to the present position.