Leave the main avenue and you are in another world

Well I was based in the city centre in Tunisia. The main avenue, Habib Borgeba which is now called 7 November, is a nice place. However, just leave it and you are in another world. The districts are poor (I might add they are relatively clean) and the streets are very narrow. Quite the contrast to the main avenue. I guess the cost of living is pretty challenging to most in the capital. I learned that there are other parts of town that are more upscale, but never was able to make it there. My unplanned schedule seemed to deter any efforts to really get a move around.