I strongly recommend this AirBnB. The loft is exactly like the pictures and very charming. The air conditioning worked great. The bed was comfortable. The location was central with plenty of sights and restaurants nearby. Pantheon was minutes away. We wish we could have stayed longer!
If you do not like stairs this may not be the place for you. It is located on the top floor. You will probably want to taxi from the train station but the fares are very reasonable (10$ or less)