The Mori ruled the Choshu domain (modern-day Yamaguchi) during the Edo period (1603–1867). After being forced to move to Hagi in 1603 they built Hagi Castle here in 1604. The castle stood for over 250 years as the center of the Mori family’s power. Situated at the foot of Mount Shizuki, Hagi Castle was designed to be especially difficult to capture—it was protected by three moats, large stone walls, several gates, countless guardhouses, and the entire upper-class samurai district. Even if attackers breached these defenses, at the very top of Mount Shizuki was a small fortress where defenders could make a final stand.

However, with the end of samurai rule in 1868—a change that the Mori helped cause—the lords of Hagi not only relinquished control of their domain and castle, but led the way in removing symbols of the past: the main tenshu, or keep, was torn down in 1874, and in following years the castle’s land was sold off by the Meiji government.

The area once occupied by Hagi Castle is designated as a National Historic Site (1951) and is registered as one of the UNESCO World Heritage Sites known as the “Sites of Japan’s Meiji Industrial Revolution” (2015). It is now open for public use as Shizuki Park.