Martina's place is perfectly situated in the center of the old town. Everything is at most a 20 min walk away, from great food, to tourist spots, to transportation hubs.
The check-in was great as Martina gave us good directions, and welcomed us quite late in the evening.
I recommend Martina's flat for anyone who wants to stroll around Napoli day and night, and have a cozy little place to crash at.