The Romans, who occupied the region 2,000 years ago, used the main valleys around the massif for military purposes. They gave the name Alpes Penninae, or Poeninae, to the highest parts of the Alps—which extended from Mont Blanc to Monte Rosa. They took over Aosta from the Salassi Celtic tribe in 25 AD and engineered roads which extended northwards into Europe via the Great St Bernard Pass and the Little St Bernard Pass.: Courmayeur, on the southern side of the massif, began to develop as a stop-off along their trans-alpine trading routes between Italy and France. Parts of the modern Tour du Mont Blanc walking trail still follow the route of a Roman road along the Col du Bonhomme and the Col de la Seigne.