Yamadera or the "Mountain Temple", as more commonly called, is easily reached in about twenty minutes by train from the city of Yamagata, Yamagata Prefecture. 
The Yamadera Temple, historic site that is within the cultural-landscape protected monuments of Japan, is a few minutes walk from Yamadera Station. 
The station is served by JR Senzan line that connects the city of Sendai and Yamagata, and you can get there either from Yamagata Station in about 20 minutes, or from Sendai station in about one hour.