CITY WALL / RING ROAD

The city has a clearly defined edge. In medieval times this would have been a hard defensive wall; today, the boundary is less distinct and more likely to be a ring road, but the principle is the same. Active and productive life can carry on within the city, in the shelter offered by the boundary.

The boundary of the city is not, however, continuous. For the city to function, materials have to both enter and leave. In some cases, such as with heavy plant and lorries, it may be sensible to prevent entry.