Konyak,
European borders are recent, populations spread out as medieval villages along trade routes mixing all the way from the Atlantic to the Caucasus. On the West edge, before radio broadcasting and central government standardized education forced conformity on populations, it was possible to move from village to village going East from Amsterdam or Rotterdam and slowly find yourself transitioning from Dutch to German. Similarly in Southern Italy the Neapolitan hinterlands were still speaking the Greek of Magna Graecea at the begining of the 20th century.