Excerpts from Books and Wikipedia
The Romans responded by building a defensive wall 12 years later. The wall around the city was 7 miles long, and some of it can be seen today. [Furtado: 1001 Days] "The Romans emerged from the Capitol to rebuild, hastily, in case the enemy should return. 'All work was hurried,' Livy concludes, 'and nobody bothered to see that streets were straight. . . . and buildings went up wherever there was room for them. This explains why . . . the general lay-out of Rome is more like a squatters' settlement than a properly planned city.' The first barbarian sack of Rome had not only smudged Rome's imperial ambitions, but left a permanent mark on the city itself." [Bauer: Ancient World, p. 561] "It set the scene for Roman anxieties about invaders from over the Alps, of whom Hannibal was the most dangerous, but not the only one. It helped to explain why so little hard information survived for early Rome (it had gone up in flames), and so it marked the start, in ancient terms, of ‘modern history’. [Beard: SPQR, p. 157]