What to do/see when in Rome (Italy) for six hours?

What are the bookends? IOW, what happens at 8am to turn you loose & at 2pm when you need to be starting whatever is next?

Here’s a recent thread on a similar situation in ORD where somebody had 3 hours from scheduled flight arrival to scheduled flight departure. They were disabused of the notion that they had any slack time at all. If you’re in a similar boat, this might be useful info to you.