Complex sentence: Cave Dale is accessed through a narrow rocky opening almost from the centre of Castleton and Peveril Castle is seen high up on the almost vertical western slopes, the Normans chose this site because the steep sides of Cave Dale gave a natural defence and good lookout.
Split into simpler sentences: Cave Dale is accessed through a narrow rocky opening almost from the centre of Castleton and Peveril Castle is seen high up on the almost vertical western slopes. The Normans chose this site because the steep sides of Cave Dale gave a natural defence and good lookout.