Fossils in the Castle Wall Stones
Fossils are sometimes visible in the hard, gray, ancient limestone (ko-ki sekkai-gan) stone used to construct the walls of Nakijin. The stone is found only in this area and was quarried both onsite and nearby. All limestone began on the seafloor eons ago as calcium-rich coral, shells, and the remains of plankton. In Okinawa it ranges from the softer varieties used in most castle walls to the more ancient and harder type used here at Nakijin. Because its hardness makes it difficult to shape and fit the stones as was done at many other Ryukyuan castles, here they were stacked using a simple method called “nozura-zumi,” which takes advantage of their natural shape. Many fossils such as this ammonite have been found embedded in the wall stones, attesting to their ocean-floor origin.