Vercingetorix chose to defend the Mandubii "oppidum" of Alesia next, in what would become the siege of Alesia. After the poor performance at Gergovia, Caesar felt a direct assault on the Gauls was no longer a viable solution, so he opted to simply siege the settlement and starve out the defenders. Vercingetorix was fine with this, as he intended to use Alesia as a trap to lay a pincer attack on the Romans and sent a call for a relieving army at once. Vercingetorix likely did not expect the intensity of the Roman siege preparations. Although modern archeology suggests that Caesar's preparations were not as complete as he describes, it is apparent that he laid some incredible siege works. Over the span of a month, the Romans built some of fortifications. These included a trench for soldiers, an anti-cavalry moat, towers at regular intervals, and booby traps in front of the trenches. The fortifications were dug in two lines, one to protect from the defenders and one to protect from the relievers. Archeological evidence suggests the lines were not continuous as Caesar claims, and made much use of the local terrain, but it is apparent that they worked. Vercingetorix's relieving army arrived quickly, yet concerted coordinated attacks by both the defenders and relievers failed to oust the Romans.