A lot of strange-shaped rocks rise along the gorge of 30 km from the river mouth of the Koza River to Shichikawa Dam in Wakayama Pref. among which the most overwhelming is Ichimaiiwa Rock (monolith). The rock, which is 100 m in height and 500 m in width, is designated as a national Natural Monument. There is a legend about this vigorous rock. Once upon a time, there lived a monster, who loved eating rocks. The monster set his eyes to the area along the Koza River and started eating rocks in this area one after another hungrily. When the monster arrived at Ichimaiiwa Rock and was just about to bite into the rock, a dog noticed it and fiercely attacked the monster. As the monster was afraid of dogs, he ran away at full speed. It is said that the bite marks of the monster still can be seen on the rock. His tears of vexation dropped on the rock and formed a waterfall named the Inyo Waterfall. The Koza River is known for cherry blossoms and autumnal leaves. Visitors can enjoy seasonal changes in the scenery.