Avaricum was situated, as Bourges is at present, at the extremity of a piece of ground surrounded, to the north and west, by several marshy streams: the Yèvre, the Yévrette, and the Auron. (_See Plate 20._) The Gaulish town, adorned with public places, and enclosing 40,000 souls, exceeded, no doubt, in extent the Gallo-Roman circuit. The aspect of the locality is certainly no longer the same: the marshes have been dried, and the courses of water reduced within regular limits; the ruins accumulated so many centuries ago have raised the level of the ground on many points. To the south of Bourges, at a distance of 700 mètres, the ground forms a neck, which, in the time of Cæsar’s wars, was narrower than at present; it inclined more towards the place, and presented, at 80 mètres from the walls, a sudden depression, resembling a vast fosse. (_See the section along C D._) The slopes, then, abrupt towards the Yévrette and the Auron, defined more clearly the only and very narrow avenue (_unum et perangustum aditum_) which gave access to the town.[471] Cæsar established his camp behind this tongue of land, to the south, and at 700 mètres from Avaricum, between the Auron and the Yévrette. As the nature of the locality prevented all countervallation, he took his dispositions for a regular siege. The place was only open to attack towards that part of the enclosure which faced the avenue, on a width of from 300 to 400 Roman feet (about 100 mètres). In this place the summit of the walls commanded by about 80 feet (twenty-four mètres) the ground situated in advance.[472] Cæsar commanded a terrace to be commenced, covered galleries to be pushed towards the _oppidum_, and two towers to be constructed. During the execution of these works, trusty messengers informed Vercingetorix every moment of what was going on in Avaricum, and carried back his orders. The besiegers were watched when they went to forage, and, notwithstanding their precaution to choose every day different hours and roads, they could not move any distance from the camp without being attacked. The Romans incessantly demanded provisions from the Ædui and the Boii; but the first showed little haste to send them, and the latter, poor and weak, had exhausted their resources; moreover, their country had just been laid waste by fire. Although, during several days, the troops, deprived of corn, lived only on cattle which had been brought from afar, yet they uttered no complaint unworthy of the Roman name and of their preceding victories. When, visiting the works, Cæsar addressed by turn each of the legions, and offered to the soldiers to raise the siege if they felt their privations too rigorous, they unanimously called upon him to persevere: “they had learned,” they said, “after so many years that they served under his command, never to suffer anything that was humiliating, and to leave nothing unfinished.” They renewed this protest to the centurions and to the tribunes.