Castle of Antirrio also known as Castle of Roumeli, is a castle in the town of Antirrio, located at the north edge of the Strait of Rio, at the entrance to the Gulf of Corinth. The castle was established by the Turks in 1499 as they understood the stratigic importance of the strait, to gain better control over them, they establishing the Rio caslte (Castle of Morea) on the opposite side. The modern Rio-Antirrio Bridge that connects by road the town of Rio on the Peloponnese peninsula to Antirrio on mainland Greece.

The Castle of Antirrio was established by the Ottoman Empire in 1499. The castle was built on several layers dating back from the midevil times. Even though it was built by the Turks, the castle has many features of Vennitian style. The castle is a typical sea front castle that has a nearly hexagonal plan featuring polygonal bulwarks at the corners. The castle is characterized by rectilinear concrete walls 4m wide, 8m successive ramparts, A notable feature is a semi-circular cordon at the base of the parapet, which extends along the outer surface of the wall. The main gate, situated on the northern side, provides access to the interior through an arched corridor. Sources from the 17th century say that within the castle there were 89 houses, a mosque, a small mescid dating to the days of Suleyman the Magnificent and a Turkish basthhouse.

The Castle of Antirrio has several notable dates in its history:

• 1499: The Castle of Antirrio was built by the Turks.
• 1532: The castle was besieged by Genoese admiral Andrea Doria. After a failed resistance, the Turks blew up the castle.
• 1533: The Turks restored and reinforced the castle as well as bringing in heavy artillery firepower from nearby Naupaktos (Lepanto).
• 1603: The castle was destroyed by the Maltese Knights. It was later rebuilt by the Ottoman Empire.
• 17th century: The Turks blew up the castle again when Doge of Venice, Francisco Morosini, forced them to abandon it.
• Late 17th century: Venetian engineers rebuilt the castle, and it remained under Venice's control until 1699.
• 1699: The castle was ceded to the Turks under the terms of the Treaty of Karlowitz.
• 1829: The castle was finally surrendered to the Greeks.
• Today the castle that has been restored by the Ministry of Culture is well preserved and is used as a touring site as well as cultural site for events during summertime.

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