The character of Marseille has been determined to a great extent by geographic location. Its natural harbor, sheltered by a semicircle of limestone hills on the Gulf of Lion and close to the estuary of the Rhône River, offered its first settlers the prospect of linking the Merranean seaways with northern Europe across a land that, in classical times, was made largely impassable by forests. The trading port founded by Greeks from the city of Phocaea about 600 BCE was to attract both settlers and visitors.