The city wall is fast disappearing in Nanjing as well and I suspect Zhonghuamen remains partly due to the fact that it's quite a good money spinner. That aside several parts of the city wall and ramparts were removed, rebuilt repeatedly in the last 50-60 years to make way for roads & cars. What remains provide an indication of what the double walled fortification was capable of, during the days of horses and spears.
Stretching from South Nanjing (Zhonghuamen) up to Xinjiekou the area was once full of excellent Ming & Qing courtyard homes - better examples than the hutongs in Beijing.
The frantic pace of development obliterated the city's historical and cultural memories, making homeless the thousands that used to live in these places.
Surrounding Xhonghuamen, there were numerous maze-like communities full of wonderful Ming & Qing architecture. They were vibrant with residents going about their daily lives, shopping, cooking, kids rushing to schools, washing hanging overhead in the lane ways, food air dried on roof tops, residents gathering under trees gossiping or playing cards. Although the houses were old and in need of repairs the residents always kept their streets clean and tidy; they had electricity and communal toilets and showers.
Unfortunately, only a couple of such streets remain and they are not great examples. Not only are the Ming & Qing architecture disappearing, I felt the sense of community has diminished too.
So if you feel inclined, I recommend a walk through the area. It is generally safe and I suggest doing it in broad daylight.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.