Ammianus Marcellinus Res Gestae 29.6.11

[11] Therefore, soon calming his fear, he roused himself with vigorous effort to meet the urgent situation. He cleared out ¹ the moats, which were choked with rubbish, and being naturally inclined to building, since the walls through long-continued peace had in great part been neglected and had fallen, he raised them even to the completion of pinnacles of lofty towers. And the work was quickly finished, because he found that the materials ² which had long since been collected for the purpose of building a theatre were sufficient for what he was hastening to accomplish. Also to this excellent plan he added another equally useful by summoning a cohort of bowmen from the nearest station, to aid them in a siege, if one should come.