Yamada Castle, Gusuku ruins in Onna, Japan

Yamada Castle is a gusuku ruin on a narrow limestone plateau about 90 meters above the west coast of central Okinawa. Excavations from 1986 to 1988 found it measured roughly 30 meters east-west by 160 meters north-south, with unpaved stone walls remaining on the east and west sides.

Yamada Castle dates from the 14th–15th centuries; its construction date is unknown. It was held by a branch of the Iha Anji of Iha Gusuku, and Gosamaru, adopted heir of the Yamada lord, is said to have made it his first residence. After joining Shō Hashi's 1416 campaign against Hokuzan, Gosamaru moved to Zakimi Castle, and in 1420 Yamada's stone walls were demolished for its materials.

The fortress displays construction methods from the Ryukyu Kingdom through its traditional stone placement and defensive layout. The wall arrangement tells of the military tactics that shaped this region's past.

The ruins are open to visitors and feature informational displays about medieval military tactics and construction techniques. Wear sturdy shoes as the terrain is uneven and involves some climbing.

The stones from this fortress were transported south to build another stronghold, creating a direct physical link between two monuments. This reuse shows how valuable resources were in medieval Okinawa.