Residenza Reale is the best apartment you can opt for to enjoy Napoli city centre.
The interiors are elegant and characteristic, and cleanness is spot on in every corner of the apartment (which is very spacious by the way).
The location is unbeatable, right behind Piazza Plebiscito and the check-in was smooth and easy. Luciano, the apartment's operator has been the kindest with us and very knowledgeable with local tips which suited our non-touristy requests. He even recommended and booked a table for us in a beautiful restaurant facing the sea: he really went the extra mile!
I highly recommend Residenza Reale and will definitely book it again once I'm back in Napoli!