Why are some districts in Shanghai so big and some so small?

Because the city center of Shanghai was not as large as it is now, the districts in the city center were divided into relatively small areas. The surrounding areas of Shanghai were originally just counties or towns, and were later planned as new central urban areas, so they were basically divided into

The original divisions of cities and counties were relatively large. In contrast, the more peripheral areas were originally suburban and rural areas, and of course the land area was larger. So if you look at the map of Shanghai, the central areas are very small.

The outer districts are very big. Pudong District has the final say, so there is nothing we can do if Nanhui is eaten up... Another point is that a district must have a series of facilities such as schools, medical care, etc. that meet certain conditions. In the central city,

The facilities are relatively concentrated, so the zones can be smaller, while the facilities on the periphery are relatively few, so the zones can be made larger.