William II of Sicily
However the first document attesting the existence of the modern city dates from circa 1000 AD, during the catepanate era of Byzantine sovereignty. The area remained marshy and unhealthy, until Robert Guiscard directed draining the wetland, boosting the economic and social growth of the city. The city was the seat of Henry, Count of Monte Sant'Angelo during the last twenty years of the 11th century. In the 12th century, William II of Sicily built a cathedral here and further enlarged the settlement.