 Following the Gallic Wars of 58–51 BC, Caesar's "Celtica" formed the main part of Roman Gaul, becoming the province of Gallia Lugdunensis.This territory of the Celtic tribes was bounded on the south by the Garonne and on the north by the Seine and the Marne.The Romans attached large swathes of this region to neighboring provinces Belgica and Aquitania, particularly under Augustus.