It was built on a base of Ryukyuan limestone and occupies 8,000 square metres (86,000 sq ft).

Agena Castle sits at an altitude of 49 metres (161 ft), and is naturally protected by the Tengan River to the north.

[3] The Ōgawa reached their greatest period of prosperity in the 15th century.

The outer gate of Agena Castle no longer exists, but as the inner gate is bored through the limestone foundation and is surround on both sides with quarried rocks, it still exists.

The castle's location now holds numerous utaki sites of worship of the Ryukyuan religion, and is scattered with fragments of Chinese ceramics from the 14th to the 15th century.