Ionian Islands in Venetian hands since 1238. The islands thus became the only part of the Greek-speaking world to escape Ottoman rule, which gave them both a unity and an importance in Greek history they would otherwise not have had. Corfu was the only Greek island never conquered by the Turks. Under Venetian rule, many of the upper classes spoke Italian (or Venetian in some cases) and converted to Roman Catholicism, but the majority remained Greek ethnically, linguistically, and religiously. In the 18th century, a Greek national independence movement began to emerge, and the free status of the Ionian islands made them
Sea of Marmara , with dimensions .Its greatest depth is . The sea takes its name from Marmara Island, which is rich in sources of marble, from the Greek "μάρμαρον" ("marmaron"), "marble". The sea's ancient Greek name "Propontis" derives from "pro-" (before) and "pontos" (sea), deriving from the fact that the Greeks sailed through it to reach the Black Sea, "Pontos". In Greek mythology, a storm on Propontis brought the Argonauts back to an island they had left, precipitating a battle where either Jason or Heracles killed King Cyzicus, who mistook them for his Pelasgian enemies. The surface salinity of the sea averages