What is the perfect size of a municipal place.

The person can't sense the earth is a round ball. All the houses and bridges are designed in a straight line. For the living circumstance, the world is flat. I calculate if someone on lowest cloud, the horizon the person can see is about 117km (70 miles) away. So the area is between 30km^2 to 40 km^2. The size of Michigan State is five times of that area. Well of course, in the US, everyone behaves like an independent person and know the size of their state(estate). At least, a person should know "my body, my castle" "my body, my estate"