Churches & museums bag requirements

I don't know of a cheat sheet. Major museums and churches vary. Check out their websites and they will tell you. Unless you need a backpack for the day, I would just leave it in the room. The only time I carry a small backpack is between cities obviously and if I am out hiking and want water and food.

We were recently in many places like you've listed, though in Spain, where my husband was either fine with his backpack on his back or he was asked to wear it in front. If no backpacks were allowed either coat check or lockers were available. Coat check was free. The lockers were usually the kind that required a euro to lock and then it was returned once you got your belongings out. In the many places we went to, those options were always available and we never were turned away. Hopefully, Italy will be similar.

There isn't any sort of cheatsheet detailing the restrictions for all Italian museums, churches and monuments so you'll just need to pull up the websites of each of them you intend to visit. I don't know if you're planning on the Borghese in Rome but if you do, be prepared to check almost everything on you, minus your phone or camera.

There are no lockers or bag-check services at the Colosseum, Palatine and Forum.

Thanks everyone! I'll look them up individually.