Complex sentence: These cliffs reputedly form the longest unbroken line of cliffs in the world; they extend for something like 400km along the Great Australian Bight near its northern extremity and are close to the Nullarbor Plain in a very sparsely settled area of Australia.
Split into simpler sentences: These cliffs reputedly form the longest unbroken line of cliffs in the world; they extend for something like 400km. They border the Great Australian Bight near its northern extremity and are close to the Nullarbor Plain in a very sparsely settled area of Australia.