This is probably the best Airbnb we've stayed in. We'll appointed, clean and despite being literally right in the action, is so quiet (double glazed windows). It's literally 20metres from Spagna metro station and 50metres from the Spanish Steps.
All of the major sights are within a 15 minute walk or a quick train ride away.
The host Sebastian is attentive and unbelievably helpful - we needed a doctor and he was straight on it for us, along with recommending all the best places to eat and visit. You could not ask for a better host.
If this place is free when you're in Rome, book it!!