The Marne (Latin: Matrona) has its source on the Langres plateau, at an altitude of about 420 metres. It flows about 514 kilometers south-east of Paris as a right tributary into the Seine.
In ancient times the river was called Matrona after the Celtic river goddess of the same name. According to Julius Caesar, the Matrona with the lower reaches of the Sequana (Seine) was the border between the Belgae people and the actual Gauls.
Source: Wikipedia