 Celtic river-names are found in great numbers around the upper reaches of the Danube and Rhine, which led many Celtic scholars to place the ethnogenesis of the Celts in this area.Diodorus Siculus and Strabo both suggest that the heartland of the people they called Celts was in southern France.The former says that the Gauls were to the north of the Celts, but that the Romans referred to both as Gauls (in linguistic terms the Gauls were certainly Celts).