Patras is a city in the northwestern Peloponnese, at the mouth of the Gulf of Corinth. Its location, astride important east-west commercial routes, and the cult of St. Andrew gave it significance.
It apparently survived the Slavic invasions, remaining in Byzantine hands. Around 805 the city was saved from an attack by Arabs and Slavs, reputedly through the intervention of St. Andrew; thereafter the Slavs were obliged to maintain officials and envoys passing through Patras so that the metropolis was exempted from this burden. The noble widow Danelis accumulated a considerable fortune there and possessed numerous slaves. She greeted Basil I as the future emperor when he was sent to Patras by Michael III on state business.
The bishop of Patras, originally suffragan of Corinth, was elevated to metropolitan rank, perhaps around 805. From that time he is identified as metropolitan of Achaia and he was able to contest control of the Peloponnese with his former superior. By the early 10th century the bishops of Sparta, Methone, Korone, and Bolaine were subject to Patras. The bishop also had unusual political and economic power.
The Crusaders took Patras in 1205 and created a barony there under the jurisdiction of the Principality of Achaia. The Latin archbishopric of Patras was established around 1207. In 1267 the last baron, William II Aleman, sold his fief to the Latin archbishop of Patras. From then until the early 15th century the bishop was effectively an independent prince. At that time Venetian influence grew and they temporarily held the city. Constantine XI Palaiologos took Patras in 1430, but in 1460 it fell to the Turks.
Near the modern Church of St. Andrew is a subterranean fountain decorated with polychrome marbles. where coins of the 4th century and a tomb were found associated with it. In addition there are a hagiasma of the 15th century and an Early Christian basilica in Patras. The fortification of the citadel was probably carried out by the 6th century, although there was considerable rebuilding in the 13th and 15th centuries.
Oxford Dictionary of Byzantium