There are 20
rioni
(neighborhoods) cut from the part of Rome within the Aurelian walls.
Two more, Borgo and Prati, form the 22
rioni of Rome.
Here's a map of the city and its sections. (I lifted this from the web,
then added detail myself.)
All of the public trash bins have handsome cast metal badges of the
rioni's symbols. Each
rione
symbol has some historical reference, most of which are obvious. Celio,
though, for instance, is as unexpected as it is fascinating.