Cameras shall not be hidden, but in Rome and in other cities, the cameras often monitor & enforce traffic restrictions rather than speed limits. Foreigners not used to such wide restricted areas - and not paying attention to the road signs! - may get fined if they misunderstand what's being monitored.

Furthermore, a number of cameras along the motorways don't check the speed in a specific time & place, but they are components of a system called 'Tutor' monitoring the average speed on long segments.

@ mike2200 - Whether you get the fine documentation forwarded to the USA - or any other country - it really depends on the local government, but relatives of mine reported mailing to Australia from Rome and Florence (and yes - because of the unauthorized access to traffic restricted zones).

@ aginsf - Nope, in Rome there's no work-around. You get fine every single time you cross the 'border' of the restricted zone, and fines are steep. No exception, basically.