The Seine is a 776 km long river and an important commercial waterway within the Paris Basin in the north of France. It rises at Source-Seine, 30 kilometers northwest of Dijon in northeastern France in the Langres plateau, flowing through Paris and into the English Channel at Le Havre. It is navigable by ocean-going vessels as far as Rouen, 120 km from the sea. Over 60% of its length, as far as Burgundy, is negotiable by commercial riverboats and nearly its whole length is available for recreational boating; excursion boats offer sightseeing tours of the Rive Droite and Rive Gauche within the city of Paris.There are 37 bridges within Paris and dozens more spanning the river outside the city. Examples in Paris include the Pont Louis-Philippe and Pont Neuf, the latter of which dates back to 1607. Outside the city, examples include the Pont de Normandie, one of the longest cable-stayed bridges in the world, which links Le Havre to Honfleur.The name "Seine" comes from the Latin Sequana.Some have argued that Sicauna is cognate to the name of Saône River. However, a suggested relationship to the River Shannon in Ireland is unlikely, given the very different forms of the two.Some believe the ancient Gauls considered the Seine to be a tributary of the Yonne, which indeed presents a greater average discharge than the Seine.Some identify the river Sikanos, origin, with the river Sequana.According to Pierre-Yves Lambert, a specialist of the Gaulish language, Sequana retains QV, that is unusual in Gaulish, which is normally a P-Celtic language, but he compares with the month name EQVOS, read on the Coligny Calendar. The name of the Gaulish tribe Sequani derives from it.The digram QV of Sequana could recover a whole syllable, that is to say,like ucuetis, but its meaning remains unknown.