A Castle on a Hill by a River

This picture was painted by a 17th-century Dutch imitator of Ruisdael. It has recently been suggested that it is an early work by Ruisdael's follower Johan van Kessel (1641 - 1680). It may be based on a lost work by Ruisdael showing Bentheim Castle on the German/Netherlandish border. The viewpoint is different from any of the known paintings of this subject by van Ruisdael.