Complex sentence: Situated on the left bank of the Rhine, Burg Rheinfels was started in 1245 by Count Diether V of Katzenelnbogen, by the late 17th century it was a fortress complex.
Split into simpler sentences: Situated on the left bank of the Rhine, Burg Rheinfels was started in 1245 by Count Diether V of Katzenelnbogen. By the late 17th century it was a fortress complex.