The Civil Wars, Book 2

While these things were going forward in Spain, Caius Trebonius, Caesar's lieutenant, who had been left to conduct the assault of Massilia, began to raise a mound, vineae, and turrets against the town, on two sides; one of which was next the harbor and docks, the other on that part where there is a passage from Gaul and Spain to that sea which forces itself up the mouth of the Rhone. For Massilia is washed almost on three sides by the sea, the remaining fourth part is the only side which has access by land.