After his defeat at the Battle of Sekigahara, Mori Terumoto moved to Hagi in 1604 and built his modern Hagi Castle. The castle was completed in 1608, and the Mori clan would rule for the next 260 years until Japan welcomed in the new era of Meiji during the time of the thirteenth domain lord, Mori Takachika. From a top Mt. Shizuki, 143m above sea level, the clan could keep watch over the surrounding area. A stronghold was also set upt here, which could sustain them through a siege in times of war.
The honmaru, main bailey, was positioned deep in the flatlands below the mountain, and contained the castle keep and daimyo's palace. The ninomaru ,outer bailey, surrounded the main bailey from three sides, and was home to the clan's facilities such as weapon towers. It also contained the family temple of the clan's ancestor Mori Motonari, and recreational area for the domain lord such as the East Garden. The honmaru and ninomaru were separated by the inner moat, and the ninomaru and sannomaru by the central moat, which has now been reclaimed. Around 1873, the castle's various structures, including the keep, where dismantled, and in 1879, a commemorative shine to the Mori clan, Shizukiyama Shrine, was fecture, and later in 1951 was designated a national historic site. In 2015, it became part of the UNESCO World Heritage Site of Japan's Meiji Industrial Revolution: Iron & Steel, Shipbuilding and COal Mining site, forming part of the Hagi Castle Town component site.