There is a dress code to visit churches in Italy: it is forbidden to enter a church (chiesa) wearing shorts or skirts above the knee, sleeveless tops, and shirts that don’t cover your belly button. Some churches display the dress code sign on the door, others do not, and some even have a person at the door to turn away those who are not dressed properly, especially at the major churches, basilicas, and cathedrals.

The worst-case scenario is that this could happen after you have been waiting in line for a long time and you realize it at the very end because the sign is displayed right by the entrance door. Just be aware.