After this important success the Athenian generals prepared at once to form the siege of Syracuse. They first constructed a fort at a place called Labdalum, on the northern verge of Epipolae, and near its western extremity, to serve as a safe depositary for their baggage and money. Then, taking up a position near the centre of Epipolae, they built a circular wall, covering a considerable space of ground, and defended on the side towards the city by an outer breastwork, a thousand feet long. This enclosure, which was called the Circle, was intended as a shelter for the men employed on construction of the blockading wall, which started from either side of the Circle, and was to be carried north and south until it reached the sea. The work made rapid progress, and greatly alarmed the Syracusans, who saw themselves in danger of being cut off from all hope of succour on the land side. Dismayed by this prospect, they resolved to make one more effort to drive the Athenians from their position, and marching out in full force, offered battle. Advancing in haste and disorder, they would certainly have suffered a crushing defeat, but for the prudent caution of their generals, who were so much impressed by the superior discipline of the Athenians, that they gave the order to retire, and led their troops back into the city, leaving only a detachment of horse to skirmish with the besiegers. But the Athenians had now an efficient force of cavalry, which had been raised by successive reinforcements to the number of six hundred and fifty men; and these, backed by a small force of infantry, soon drove the horsemen of Syracuse from the field.