Naples

I liked Hotel Piazza Bellini, a short walk from the archaeological museum and centro historico (others recommend the waterfront).
For things to do, I'd check out https://www.napoliunplugged.com/ and consult a Blue Guide. Seeing a Caravaggio (https://www.visitnaples.eu/en/neapolitanity/discover-naples/caravaggio-three-neapolitan-masterpieces) and touring the underground will be on my agenda when I get back.

For near the waterfront in Chiaia area, we enjoyed staying at Palazzo Alabardieri.

Orsini46 B & B is excellent, well-located, but has only 3 rooms, and is very popular and often fully-booked. When are you traveling?

I second valadelphia's suggestion of the Hotel Piazza Bellini. The staff are friendly and helpful, and the interior courtyard where breakfast and aperitivi are served is a welcome peaceful spot after a long, hot day of sightseeing. I stayed there 4 nights in May.

For me, the absolute highlights of Naples were:

1) the Cappella Sansevero, with the astonishing sculptures (the Veiled Christ is most famous, but I found Disillusion even more amazing), and the creepy Anatomical Machines in the basement. https://www.museosansevero.it/en/

2) the Archeology Museum, with the massive sculptures from the Baths of Caracalla and the paintings and mosaics from Pompeii and Herculaneum (almost everything on site is a reproduction; the originals are here). https://mann-napoli.it/en/home-english/

Do you have Rick's Italy book? He has a very good chapter on Naples, with a walking tour.