The move of the Mori from Yoshida Koriyama to Hiroshima was but one of many transitions as the new era began. River mouths provided sites which met economic criteria and allowed the deployment of water for defence and movement but were vulnerable to natural disaster. At Hagi, the form of the delta predicated the location of the castle at the foot of Shizukiyama for sound topographical and defence reasons. Along the higher ground stretching along the seafront from Shizukiyama to Hamazaki were substantial stands of trees. Hagi-ura was an inlet at the delta of the Amu River where it flowed into the Japan Sea. The delta area around Hagi was occupied in the second half of the sixteenth century by the Mori retainer, Yoshimi Masanori, lord of Tsuwano in Iwami, who built the temple Zenpukuji and a villa for his retirement at the base of Shizukiyama on the site of the future castle.