Complex sentence: It is also called "the fort of the rounded hills" or the "fort of the goats," and sits on a high hill overlooking Doolin and, along with a nearby radio mast, is used as a navigational point by boats approaching Doolin Pier.
Split into simpler sentences: It is also called "the fort of the rounded hills" or the "fort of the goats". The castle sits on a high hill overlooking Doolin and, along with a nearby radio mast, is used as a navigational point by boats approaching Doolin Pier.