Rome in two days:
You can pass a lifetime in Rome and, still, not know everything about the eternal city. You can get a good understanding by visiting for a week or more, but if you have only 48 hours, you must be willing to experience as much of Rome as possible.
You can rely on a tour operator to put you in a group as sheep, or you can pay through the nose for a private guided tour. You can also organize your time, searching the internet for all the information you need.
Unfortunately, most of the information you get in this way reflects the incredible amount of money the operators active in the tourism business are spending to end up at the top of the search results page.
Sometimes you could find a result saying that the church or museum you are interested in is not free to visit; it’s available only through some guided tour. Suppose you have the patience and the know-how. In that case, you could instead discover on page ten of the results that the official website of the church or museum says precisely the opposite, and it is free, or there is a minimal charge for some service, like the audio guide, or the elevator access to the roof.
I did all this research on your behalf for this booklet, and I included the results in my writing.