How did the Romans manage to effectively combine their whole empire into one unit

Through the many connections that Rome had, it made it easier for the Whole empire to be one Unit. The Roman Empire really started to flourish after the death of Julius Caesar in 44 B.C.E and during Augustus's rule which was mainly during the Pax Romana or the peace that existed between all the nationalities within the Roman Empire. For one thing, Rome had an enormous population. Julius Caesar granted whole towns and cities outside of Rome Citizenships and during the reign of Augustus the increase of the citizen roll was approximately 900,000! The peak of the amount of citizens in Rome was approximately 100 million people. Citizenship helped to Romanize the empire. In modern day society towns, cities and states are connected by many roads and this is quite similar to what the Romans valued. The total mileage of roads in Rome is at an estimated 47,000. The empire was 2000 miles from north to south and 3000 from east to west . These roads helped connect the whole empire to the city of Rome itself. As the Roman empire reached out so did the roads.
As we studied Jared Diamond we learned about how important the placement of a civilization is. The Romans used their location to their advantage. In 30 B.C.E the Romans conquered egypt enabling them to use the rich silt that was in the nile and other various rivers and Rome was able to have many different minerals to trade because of the placement of their empire. Not only that but if you look at a map of the Roman empire you can see that it surrounds the Mediterranean in an oval and this makes trade and contact for all of the City-states a lot easier. In conclusion the population, roads, location and size of the Roman empire most definitely helped the Romans effectively combine their whole empire into one unit.