We are thus reduced to the third of the great provinces into which Gaul was divided in Cæsar's time, to try and find the people who could have erected the stone monuments of France, and at first sight it seems extremely probable that they were erected by the Aquitanians. Both Cæsar[384] and Strabo[385] distinctly assert that the people of the southern province differed from the Celts in language and institutions as well as in features, and add that they resembled more the Iberians of Spain than their northern neighbours. When, however, we come to look more closely into the matter, we find that the Aquitania of Cæsar was confined to the country between the Garonne and the Pyrenees, and where, however, few, if any, dolmens now exist. They are rather frequent in the Pyrenees[386] and the Asturias, where remnants of the dolmen-building races may have found shelter and continued to exist after their congeners were swept from the plains; and there are one or two on the left bank of the Garonne, but except these there are none in Aquitania proper. If, however, we apply the term Aquitania to the province as extended by Augustus up to the left bank of the Loire, we include the greater part of the provinces where dolmens are found; but here again, when we look more closely into it, we find that the northern districts of this great province were, in Augustus' time, inhabited by Celts, or, at all events, that Celts formed the governing and influential bodies in the states. Indeed, the fact seems to be that, during the six centuries which elapsed between the invasions of Italy by the Gauls and the return invasion of Gaul by the Romans, the Celts had gradually extended themselves over the whole of central France from the Garonne to the Seine, and had obliterated the political status of the people who had previously occupied the country, though there is no reason to suppose they had then at least attempted to exterminate them. It must thus be either that the Celts were the builders of the dolmens, which appears most improbable, or that there existed in these provinces a prehistoric people to whom they must be ascribed.