Yashima Castle

In detail

Yashima Castle was built in 667 and was one of the earliest structures on the island. It is mentioned in the Nihon shoki (completed in 720), the oldest official record of Japanese history, but the site was identified only in 1998.

The castle was established as part of a network of forts built to guard against an invasion by the kingdoms of Tang China and Silla on the Korean Peninsula—an attack that never came. At the time the fort was built, Yashima was completely separated from mainland Shikoku, and it had a commanding view of the sea. Unlike the typical castles of later periods, the fort’s layout and stone foundations, including a roughly six-meter-high stone wall, suggest it was built in the rustic style of Korean forts.

The fort’s gate on the southern slope of Yashima faces the city of Takamatsu. It has been excavated, restored, and opened to the public. The gate itself is 2.5 meters above the approach, and anyone attempting to enter must use a ladder. There is a second entrance at right angles to the main gate, creating a bottleneck for would-be attackers, called an ojo.

The fort was designed to take maximum advantage of its environment. The walls span approximately 7 kilometers, and it is thought that only 10 percent of the walls were artificial. The rest likely incorporated natural ridges and rock formations, and some of the modern-day walking trails on Yashima are thought to run on top of what were once fort ramparts.