This map shows Hippo Regius (modern Annaba), Cirta (modern Constantine, the ancient capital of Numidia), Carthage (the capital of what Romans called Africa, roughly modern Tunisia), Rome, and Milan.
Hippo Regius was located in the middle of a coastal plain with fairly easy travel along (or near) the shore for about 100 km to the east and 100 km to the west.
Then, in both directions one hits steep mountains, taxing to climb even by car. Surely the most convenient mode of travel beyond the plain was by ship along the coast.
It’s not far to the south (about 35 km from Hippo Regius) until one meets the foothills of the Aurès Mountains. From this point there is a steady and sometimes rapid incline as one enters the highlands where many prominent Numidian cities were.
Google Map’s recommended route from Hippo Regius to Thagaste
Hippo Regius provided what may seem like an immediate connection to the Mediterranean for highland cities in the eastern sliver of Numidia like Thagaste (modern Souk Ahras, where Augustine was born, about 100 km from the coast) and Madauros (modern M’Daourouch, where Apuleius was born, another 30 km south of Thagaste). But the mountains were a real obstacle that cut the highlands off from the coast.
Once in the highlands, however, the terrain is generally flat, and travel is much easier between interior Numidian cities than it is down to the coast.
In the Roman period, Hippo Regius, Thagaste, and Madauros were sometimes in a province with “Africa” in its name (i.e. Africa Nova, Africa Proconsularis), sometimes in the province of Numidia, and sometimes in both Africa and Numidia depending on the type of province in question. In late antiquity, they were part of the civil province of Africa Proconsularis but the ecclesiastical province of Numidia.
In short, administrative borders are often arbitrary and uninformative in terms of a region’s identity. Perhaps a more meaningful distinction is between coastal communities, like Hippo Regius and Carthage, linked via the Mediterranean, and interconnected highland communities, like Thagaste, Madauros, and Cirta, that lacked the same interest in the sea.
Consider Augustine, born and raised in Thagaste. He studied at Madauros for a period as an adolescent. Then he moved to Carthage, the second largest Mediterranean city in the west after Rome. He studied there for a few years, returned home for another few years, then went back to Carthage to teach for the better part of a decade. From there, he moved to Italy—first Rome, then Milan—where he lived for five or so years. He was clearly drawn to the international world that Rome’s Mediterranean offered.
While in Milan, at the age of 32, Augustine converted to Christianity and retired from public life. Presumably, he could have moved anywhere. He chose Thagaste. He didn’t simply move home to Africa. He specifically moved out of the Mediterranean’s reach, even though he was just a short 100 km south of the coast in the Aurès.
After his son died, Augustine was reluctantly pulled back into public life, moved to Hippo Regius, and became bishop there. He must have felt bitter about returning to the Mediterranean world that he had happily quit. Or perhaps it was a comfortable middle ground between the peace he found in the highlands and the energy of a major cosmopolitan port like Carthage. Either way, one thing is for certain: he was happy not being in Italy, and he never returned to Europe.