Final answer:
The Roman Empire, at its peak, controlled territories across Europe, Africa, and parts of Asia, incorporating many regions and cultures into its dominion through military conquest and unifying infrastructure.
Step-by-step explanation:
The Roman Empire was vast and conquered a multitude of territories. By 117 CE under Emperor Trajan, it had reached its greatest size, including most of England, across to Germany and Romania, and encompassing all of North Africa from present-day Morocco. The Empire extended as far east as the borders of the Parthian Empire, with only the Persians recognized as a civilization outside their domain. Significant conquests included Greece, Egypt, Sicily, Sardinia, and parts of Arabia. Rome's expansion was motivated by securing resources, and its military campaigns often resulted in the taking of slaves, who became an essential part of the Roman economy.
Through military might, Rome subjugated many cultures, creating a homogeneous empire known for its architectural and engineering achievements, which included roads, aqueducts, coliseums, and public baths. Rome's encounters with other powers like Carthage, the Macedonians, the Seleucids, and the Gauls led to various regions being absorbed into the empire at different times. Figures such as Julius Caesar played a pivotal role in the conquest of territories like Gaul. The Romans established their presence in the Mediterranean and beyond, blending and sometimes erasing the local cultures and political systems of the conquered lands.