History of the Republic of Venice of the Sea" ceremony was established in this period. Orseolo died in 1008. Venice's control over the Adriatic was strengthened by an expedition by Pietro's son Ottone in 1017, by which time Venice had assumed a key role in balancing power between the Byzantine and Holy Roman Empires. During the long Investiture Controversy, an 11th-century dispute between Henry IV, Holy Roman Emperor and Pope Gregory VII over who would control appointments of church officials, Venice remained neutral, and this caused some attrition of support from the Popes. Doge Domenico Selvo intervened in the war between the Normans of Apulia and
Gulf of Patras of 350–400 km. The port city of Patras lies to the southeast and is the only major port on the gulf. It serves ferries to Ancona and Brindisi in Italy and to Cephalonia. On the northern shore Missolonghi also has a port. The old ports of Rio and Antirrio lie at the east end of the Gulf; there is a ferry service between them which complements the traffic over the Rio-Antirio bridge. The gulf is rich in fish as well as molluscs including sea snails and clams. A number of major naval battles took place in the Gulf of Patras: