 According to the "Recueil des Inscriptions Gauloises", more than 760 Gaulish inscriptions have been found throughout present-day France – with the notable exception of Aquitaine – and in Italy, which testifies the importance of Celtic heritage in the peninsula.In 391 BC, Celts "who had their homes beyond the Alps streamed through the passes in great strength and seized the territory that lay between the Apennine mountains and the Alps" according to Diodorus Siculus.The Po Valley and the rest of northern Italy (known to the Romans as Cisalpine Gaul) was inhabited by Celtic-speakers who founded cities such as Milan.