XII. Vercingetorix, after the defeat of his cavalry, decided on a retreat; taking his infantry with him, without returning to his camp, he marched immediately towards Alesia, the _oppidum_ of the Mandubii. The baggage, withdrawn from the camp, followed him without delay.[519] Cæsar ordered his baggage to be carried to a neighbouring hill, under the guard of two legions, pursued the enemies as long as daylight permitted, killed about 3,000 men of their rear-guard, and established his camp, two days afterwards, before Alesia.[520] After having reconnoitred the position of the town, and taking advantage of the disorder of the enemy, who had placed his principal confidence in his cavalry, which was thrown into consternation by its defeat, he resolved to invest Alesia, and exhorted his soldiers to support the labours and fatigues of a siege with constancy. Alise-Sainte-Reine, in the department of the Côte-d’Or, is, undoubtedly, the Alesia of the “Commentaries.” The examination of the strategic reasons which determined the march of Cæsar, the correct interpretation of the text, and, lastly, the excavations lately made, all combine to prove it.[521] Ancient Alesia occupied the summit of the mountain now called Mont Auxois; on the western slope is built the village of Alise-Sainte-Reine. (_See Plates 25 and 26_.) It is an entirely isolated mountain, which rises 150 to 160 mètres above the surrounding valleys (_erat oppidum Alesia in colle summo, admodum edito loco ..._). Two rivers bathe the foot of the mountain on two opposite sides: they are the Ose and the Oserain (_cujus collis radices duo duabus ex partibus flumina subluebant_). To the west of Mont Auxois the plain of Laumes extends, the greatest dimension of which, between the village of Laumes and that of Pouillenay, is 3,000 paces or 4,400 mètres (_ante oppidum planities circiter millia passuum III in longitudinem patebat_). On all other sides, at a distance varying from 1,100 to 1,600 mètres, rises a belt of hills, the plateaux of which are at the same height (_reliquis ex omnibus partibus colles, mediocri interjecto spatio, pari altitudinis fastigio oppidum cingebant_). The summit of Mont Auxois has the form of an ellipse, 2,100 mètres in length, and 800 mètres broad in its greatest diameter. Including the first spurs which surround the principal mass, it is found to contain a superficies of 1,400,000 square mètres, 973,100 mètres of which for the upper plateau and 400,000 mètres for the terraces and spurs. (_See Plate 25_.) The town appears to have crowned the whole of the plateau, which was protected by scarped rocks against all attack.[522]