Complex sentence: It is the most southerly island of the Tuscan Archipelago and was known as "Dianium" by Romans and "Artemisia", "Αρτεμησία" by Greeks.
Split into simpler sentences: It is the most southerly island of the Tuscan Archipelago. Was known as "Dianium" by Romans and "Artemisia", "Αρτεμησία" by Greeks.