A pair of suspicious-looking cats in RomeA combination of the high rate of abondoned animals and the low rate of neutering mean that there are Rome has a huge population of stray and feral cats. Estimates vary, but it's believed there are several hundred thousands cats living wild among the monuments and suburbs of Rome.
While some cats are strays, still relatively domesticated, others are completely feral. They keep themselves to themselves, occasionally getting into fights with neighbourhood dogs, and are best left to their own devices.
They congregate in wastegrounds and among the ruins, especially at places like Torre Argentina, where a cat sanctuary has been set up for them (see below). Self-appointed cat feeders leave food in car parks and other spaces.
Sometimes you'll see a cat with the tip of its ear cut off: this means that at some point, the cat's been caught and neutered.
Cat Sanctuaries
Rome has several sanctuaries where the strays are fed and taken care of. One is Torre Argentina, the large open-air excavation a few minutes' walk from Piazza Venezia. This sanctuary, which has been established for around fifteen years now, is always on the lookout for volunteers, or people to adopt (or foster) cats. For more information, see their website: Roman Cats.
There's another sanctuary at the Protestant Cemetery.