Ninomaru Sumiyagura Corner Towers one of the corner turrets that existed within Mito Castle.
The main turret consists of a two-story corner turret and two turrets connected to its north and east sides, and when viewed as a whole, it forms an L-shape.

Originally, there were four corner turrets built inside the castle. These turrets were placed more on the southern side (the side facing the castle town) than the northern side, suggesting that they were designed with the view from the town in mind when looking up at the castle.

The turrets currently visible have been restored to their appearance from the Tenpo era, based on findings from past excavation and historical research, and are located in the same place as they were originally.