All of the suggestions are great. Let me ad one more: Castellabate, south of Naples in Calabria region, not far from the Greek temples at Paestum. Joe Biden, while as VP, took his wife Jill there to celebrate her 60th birthday as I recall. They stayed in the little waterfront town of Santa Maria di Castellabate. We stayed in the old hill town of Casellabate above. Had our best dinner ever (I love tomatoes and they created a special fish dinner loaded with roasted tomatoes). We also purchased our landlord's excess olive oil supply, olives picked and pressed while we were there. If you are brave, some of the most spectacular coastal driving is to the south, all the way to Maratea and its landmark Rio-like Christ statue. Blue zone towns (lots of 100+ year-olds) of Pioppi and Acciaroli, and a Mediterranean diet museum along the way.

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Castellabate


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Castellabate

mbrevitas mentioned Sperlonga and Gaeta, among others. We enjoyed both as shoulder season destinations. Sperlonga has a rare for Italy long walking beach. Gaeta was extra scenic. We stayed in the old town of Sperlonga and found people super friendly. We cooked at home and found the most huggable ladies in a little grocery store who gave us small quantities of things like dish liquid. They really made us feel welcome.
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Sperlonga


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Gaeta

Sardinia is off the radar for most people, but another great spot for better spring weather. We stayed in Alghero and Cagliari, two very different places. Our trip report is here: https://www.fodors.com/community/eur...tober-1659806/