Muryokoin Temple was constructed by Hidehira, the 3rd lord of Oshu Fujiwara. In the 12th century, it was a beautiful temple and almost entirely a copy of Uji's Byodoin, theh location of the famous Phoenix Hall in Uji, Kyoto.
At that time the Phoenix Hall was respected as the Amida's Pure Land, so that those who doubled, including children, were encouraged to visit the temple in Uji. In the same way, Muryokoin was also regarded as representing Amida's Pure land. Both temple were decicated to Amida Nyorai who was believed to be the lord of the Pure Land in the west.
Around the week of the spring and Autumn equinoxes, the setting sun is aligned with Mount Kinkei, which is just behind the temple, in this beautiful landscape, the Amida Hall,silhouetted against the sunset was the Pure Land which Hidehira intended.
(reference: official board on the site)