Mount Zaō is a complex volcano on the border between Yamagata Prefecture and Miyagi Prefecture in Japan. It consists of a cluster of stratovolcanoes and is the most active volcano in northern Honshū. The central volcano of the group includes several lava domes and a tuff cone, Goshiki-dake, which contains a crater lake named Okama. Also known as the 'Five Color Pond' because it changes color depending on the weather, it lies in a crater formed by a volcanic eruption in the 1720s. The lake is 360 metres (1,200 ft) in diameter and 60 m (200 ft) deep, and is one of the main tourist attractions in the area.