Ryukyuan Castles, known as gusuku, are great surviving ruins to the prosperous eras of the thirteenth to sixteenth centuries, when Ryukyu progressed from isolated domains to a united kingdom that enjoyed independence and extensive overseas trade. Only a few historical records have survived , so many questions about their construction and use remain unanswered. Gusuku appear to have been both defensive and spiritual in nature, with military, residential, and ceremonial facilities. All have remarkable undulating walls of Ryukyuan limestone, and though little to nothing remains of the original wooden structures, archaeological research gives us a good idea of the size and layout of the most important buildings and the lifestyles of their inhabitants.

The construction of stone castles in Okinawa began about one hundred to two hundred years earlier than in the main islands of Japan. Both Japanese and Ryukyuan castles are divided into a sequence of secure enclosures, or wards, with the most secure one at the highest elevation. But Ryukyuan castle walls are usually undulating and organic in form, while those of Japan’s castles are more strictly rectilinear with sharp corners. Japanese castles also generally featured large multistory defensive towers built of wood, which those of Ryukyu did not have.

In addition to Nakijin Gusuku Ruins, prominent surviving castle ruins in Okinawa include Shuri Gusuku, Nakagusuku, Katsuren Gusuku, and Zakimi Gusuku, all of which are World Heritage sites.