This is one of the myriad feral/stray cats of Rome. Large numbers of them inhabit the Coliseum, the Palatine Hill, the Forum and other ruins and places in the city center. We were told that a charity feeds them lots of pasta, which might sound nice, but it does not meet a cat's nutritonal needs. I hope they add vitamins or protein or something similar.
The cats were not friendly. They tended to stay away by themselves. Astonishingly enough, there are estimated to be 300,000 feral cats in Rome living in over 2000 colonies (http://goeurope.about.com/cs/rome/a/rome_cats.htm).
You will see some of the other cats in later entries in this blog, but not all 300,000.