I'm currently Interrailling through Italy, and in Rome right now, which is great, but I know I will be fed up with big cities in a few days.

Can anyone suggest a destination that's a nice and cozy place in beautiful nature, maybe has routes for day hikes and of course is reachable by train? Maybe even concrete guest houses/bed& breakfasts/hotels? Or just a general region?

We want to be in Napels later during the trip, so especially that direction would be useful!