The town on the three rivers – the Danube, the Inn and the Ilz – got its name from the Roman fort of Batavis. After 739 AD Passau grew to become the biggest bishopric on the Danube, its domain extending all the way to Hungary. After the great fire of 1662 the prince bishops rebuilt the town in the Baroque style. One of the highlights of the Old Town is the beautiful Cathedral of St Stephan, which boasts the biggest church organ in the world. High up above the town and the rivers stand the Veste Oberhaus Castle and the Maria Hilf Abbey, both of which are also well worth a visit.