The ruins of Nakijin castle are located in the northern part of Okinawa Island in the Imadomari area of Nakijin Village. At an elevation of 100 meters, it is a mountain castle built on limestone cliffs and was the fortress of the northern Hokuzan kings.

The castle has nine fortified stone walls with a central donjon. The western face of the castle is the main gate, and heading east it gets taller. Passing through Heiro Gate into the second stone enclosure are the remains of the northern headquarters. To the left and right are Umiya gardens and the Uchibaru, and one arrives in a loop at the highest point. The stone enclosure on the east side widens and shortens and is called the "Shikema."

The ramparts are evenly laid Ryukyuan limestone and are piled three meters high at the lowest and eight meters high at the highest place. The total length exceeds 1.5 kilometers. On top of the walls is a further 90-centimeter parapet, 60 centimeters thick, to function as a further layer of defense.

Archeological studies on the stone enclosure called Shikema detected an older structure, and many artifacts were unearthed. Research is progressing on the discovery of the real shape of the ruins of Nakijin Castle.