Below is an overview of the major cities in the Roman world. Besides being leading centers of commerce, local politics, religion, and culture, and being home to more citizens than any other cities in the Republic, each one has certain roles within the national community that may be distinct from the roles of other urban centers.
This information may help situate the reader in the world or even fuel backstories [since only so much can be written here while keeping things brief, I heavily encourage asking questions directly to get more details on anything here that is of interest]:
On the whole, there are seven major cities that together form the capital of the Republic. Without getting into detail, the following cities are distinguished from others by their status, the presence of the most powerful political figures, stricter laws on carrying edged weapons, and attention given to them through state funding. The word for this region of seven capital cities is the Pomerium, a term that admits no good translation into other languages.
- Rome: Home of the Roman Senate and the First Citizen of the Republic – in addition to nearly 3 million citizens. A model to other towns in its infrastructure and public services. All of the wealthiest Roman citizens have been here and many have a home somewhere near its original center.
- Byzantium: Home of the State Treasury and many of the largest commercial guilds. More money flows through this cosmopolitan city than any other, by several orders of magnitude. Most trade on the Danube and in the Black Sea is influenced by Byzantium.
- Alexandria: Home of the greatest universities and academies in the Republic, making it a center for scientific, philosophical, religious, and (nowadays) arcane research. Most of the diplomacy between Rome and Asian or African kingdoms is conducted through Alexandria. The Musaeum of Alexandria is the original university, others being named and modeled in its image.
- Carthage: Home of the military high command for the Republic and the academy for training officers in the Legion (army) and Classis (navy). Most of the managing for supplies of the army and navy is also done here. A great deal of military research is conducted in the Technaeum of Carthage, the original engineering academy.
- Antioch: Hub for land trade with Asia, especially with Islamic Persia and lands around the Oxus river valley. Primary outpost for military operations in Persia, supplanted only after the recent retaking of Armenia. Major site for the Christian Church but also the starting point for the renewal of many polytheistic religions from Ancient Asia and Africa.
- Parisium: Hub for artistic and academic discourses, rivaled only by Alexandria. Starting point of the Gallic revival, a movement in architecture, art, philosophy, and religion. Most trade in Britain and Gaul is influenced by Parisium.
- Virunum: Hub for land and maritime trade throughout Roman Germany, the Germanic Kingdoms, and Scandinavia, situated on the Albis River Hamburg. Since Roman Germany is politically insulated from Mediterranean commerce and politics, Virunum has become the center for Roman affairs in this region.
Cities outside the Pomerium may be important in their own rights and some still hold significant regional or national influence.
- Athens: Home of the Lyceum – the leading school of geology – and some of the great universities and academies of the Republic. Overshadowed by Alexandria and Parisium for philosophy and science, and by Byzantium for Greek cultural traditions. With the rebirth of the Ancient Greek religion, Athens has become its focal point alongside the strictly religious site of Olympia.
- Londinium: Hub of trade between Britain and Gaul, making it closely connected to Parisium. Largest city that has a substantial number of followers of the revived Druidic traditions that are becoming common in Britain.
- Roma Atlanta: Provincial capital of the colonies in the New World. Site of major construction projects and recent financial support from Rome.
“Ancient Map”, giving some indication of where cities are located: https://upload.wikimedia.org/wikipedia/commons/b/bb/Roman_Empire_125.png for reference.