Gaul is used to illustrate how the political insecurity of the Roman Empire altered the physical organization of towns. Its settlement pattern offers a concise contrast between the relative security associated with Roman expansion and the defensive priorities that emerged as instability grew.

Settlement Before and During Roman Expansion

Before Rome arrived in Gaul in 125 BC, settlements were commonly built on hilltops, where they were easier to defend. After Roman expansion into the region, settlements moved down to the plains. The shift marked a change in the conditions under which communities organized their living spaces: the plains had become viable as Roman power extended into the area.

The Third-Century Reversal

By the third century AD, every sizeable city in the Roman Empire had a defensive wall. In Gaul, the earlier movement to the plains was reversed, and settlement returned to hilltops. The sequence connects a visible change in where people lived with a wider deterioration in security: cities fortified themselves, sometimes using stone taken from monuments, while Gaul’s settlement pattern once again favored defensible heights.

Significance in the Roman Imperial Decline

Gaul’s changing settlement pattern is presented as material evidence of political instability, rather than as an isolated local development. The return to hilltops echoes the defensive logic that had shaped settlement before Roman arrival, showing how insecurity under the empire could undo an earlier spatial change. In the book’s account, the fortified cities and the reversal in Gaul belong to a broader pattern of declining stability across the Roman world.