- Capital
- Rome : full-fledged until Diocletianic times, from then on mostly only de jure . Mediolanum and Ravenna : Imperial residences; de facto capital in the Late Empire (of the whole Empire or only the Western part)
- Common languages
- Latin
- Religion
- Roman polytheism , followed by Nicene - Chalcedonian Christianity
- Government
- Mixed constitution
- Legislature
- Senate and People of Rome
- Historical era
- Ancient history
- Ad 1
- Estimates vary from 4 to 10 million ( c. 1 million in Rome)
- Iso 3166 code
- IT