Rioni of Rome Italy :1. Monti
2. Trevi
3. Colonna
4. Campo Marzio
5. Ponte
6. Parione
7. Regola
8. Sant'Eustachio
9. Pigna
10. Campitelli
11. Sant'Angelo
12. Ripa
13. Trastevere
14. Borgo
15. Esquilino
16. Ludovisi
17. Sallustiano
18. Castro Pretorio
19. Celio
20. Testaccio
21. San Saba
22. Prati
Rome is also divided into differing types of non-administrative divisions. The historic centre is divided into 22 rioni, all of which are located within the Aurelian Walls except Prati and Borgo.
The Rioni have changed in number throughout history, from ancient Rome, the medieval period,[49] to the Renaissance. They were later organized in a more precise way by Pope Benedict XIV in 1743.
Even after Napoleon I lost his power in the city, there were no sensible changes in the organization of the city, until Rome became the capital of the new born Italy. The needs of the new capital caused a great urbanization and an increase of the population, both within the Aurelian walls and outside them. In 1874 the rioni became 15 adding Esquilino, obtained taking a part from Monti. At the beginning of the 20th century some rioni started being split up and the first parts outside the Aurelian walls started being considered part of the city.
In 1921 the number of the rioni increased to 22. Prati was the last rione to be established and the only one outside the Aurelian walls.
The latest reform, which is still mostly valid, was made in 1972: Rome was divided in 20 circoscrizioni (later renamed municipi, one of which has since become an independent municipality) and all the 22 rioni (thus the historical center) were placed in the first one, Municipio I.