Marta's flat is fantastically located for a short walk to many great locations in the heart of Rome. It is in Trastevere, the area of small lanes with many cafe's and restaurants, but is only a couple of hundred metres from Isola Tiberi the island in the Tiber, over which is the Forum, Capitoline, and so many others. It was completely clean and functional, chic and had everything we needed. Marta is really helpful and nice.
From Fiumicini Airport, we took a train to Trastevere station and then tram 8 from right outside the station to Tram stop Belli (tickets from any nearby street kiosk) which is right by the bridge to the Isola, so maybe 2-300 metres walk to the flat. The flat is on the top floor up stairs, so if you have trouble with stairs, look elsewhere, but if you are OK with them then the rooftop view is a bonus. We had a lovely warm time in mid February.