Complex sentence: It forms the central part of the eastern shore, from the south of Hammamet to Mahdia: therefore it includes Monastir, Mahdia and Sousse the previous is its main town called "the Pearl of the Sahel".
Split into simpler sentences: It forms the central part of the eastern shore, from the south of Hammamet to Mahdia. Its main town is Sousse, called "the Pearl of the Sahel".