 The first cathedral and the residence of the bishop were built on the east end of the island at about the same time.The Romans had built their city on the Left Bank, because it was of higher elevation and less prone to flood; the forum was located on a hill about high, later called the Montagne Sainte-Geneviève after the patron saint of the city.In the early Middle Ages, the hill became the site of two important monasteries, the Abbey of Saint-Victor and the Abbey of St Genevieve, while another large and prosperous monastery, the Abbey of Saint-Germain-des-Prés, was built in the fields along the Seine farther west.