Sendai-daira is a mountain consisted of limestone within the Abukuma granite area. It makes a longitudinal flat ridge two kilometers long, at about 850m above the sea level. There are four small dolines at its northern part and a small karrenfeld has developed on its eastern slope near the flat top covered with thick residual red soil. The existence of two blind valleys near the southern foot of the mountain suggests a connection with the underground stream at the “Irimizu” limestone cave. The cave opens at the western foot of the mountain. It is about 700m long, of which the last 300m is not easily accessible.