The human presence in prehistoric times is attested by findings of lithic industry especially in Eure and Calvados. The cave of Gouym near Rouen has wall engravings and is the northernmost decorated cave in Europe. Numerous megalithic monuments are also visible in the area. The situation in Celtic times is better known, thanks to quite abundant and well dated archaeological sources. Already in the 19th century, Abbot Cochet, a local scholar, had begun to study archaeological remains, mainly in Upper Normandy, among which we can mention some remarkable discoveries, such as the golden Gallic helmet of Amfreville-la-Mi-Voie, from the 4th century B.C., or the iron helmet of the Louviers museum, or sites such as the great necropolis of Pîtres, in the Eure, with its funerary urns, swords and traces of tombs with war chariots. Between the 4th and 3rd centuries B.C. the Celtic populations of the Belgians settled in the region in successive waves, and the testimony of Caesar's De bello Gallico allows us to identify the different peoples and their oppidals in the mid 1st century B.C. Among them the Kaletians (Lillebonne or Juliobona), the Veliocassi (Rouen or Rotomagus), the Diablinti, the Baiocassi (Bayeux or Augustodurum), the Lexovians (Lisieux or Noviomagus) and the Aulerci Eburovici (Évreux or Mediolanum). Other centres were Breviodurum (Brionne), Caracotinum (Harfleur), Augusta (Eu). During the Second World War Normandy was one of the two starting points (together with Provence) of the allied offensive that ended the Nazi occupation. On 6 June 1944, Operation Overlord was launched, the largest landing in all military history, conducted simultaneously on several beaches of Calvados and the English Channel. Troops from the United States, Great Britain and Canada and French and Polish contingents took part in it. The landing was the beginning of the Battle of Normandy, which ended only on September 12 with the surrender of the garrison at Le Havre, when several regions of France had already been liberated.