The federal principle of government.
And federal means pertaining to or of the nature of a union of states under a central government distinct from the individual government of the separate states
Answer:
Building a large network of roads and bridges
Explanation:
The Roman Empire built roads, bridges to connect and expand their empire in larger extend. The roads were often brick and included channels along the sides to prevent water from ruining roads. Romans also built bridges to connect between the city and its territories across rivers.