Complex sentence: Agropoli remained in the hands of the Byzantines until 882, when the town fell to the Saracens, who turned it into a formidable stronghold (Arabic: "rabat").
Split into simpler sentences: Agropoli remained in the hands of the Byzantines until 882, when the town fell lo the Saracens. They turned it into a formidable stronghold (Arabic: "rabat").