Kavala

With a brief visit like this you will naturally find yourself going directly to the old town and the aqueduct. From there it would be easy to spend your whole day within the old town unless you want to go to the beach.

On the hill there is the acropolis (castro, castle) and nearby is the Mehmet Ali Museum and Residence.

Head-poking along the narrow streets, having lunch at a taverna, and then perhaps retire before re-boarding at Eleftherias Square, which I presume will be near to your ship.

Everyone who goes to Kavala loves it and I expect just covering ground there will be very pleasing.

Thanks for the update on Kavala. I love exploring side streets and people watching.

There’s a free hourly mini train which runs up to the castle. Might be worth considering taking the train up and walking down if you only have a day.

https://www.visitkavala.gr/en/sightseeing/metakinisi-sti-poli/

Mermaids and Guys in Ellis Street, one of a cluster of backstreets as you come off the hill of the old town, is worth considering for lunch.

The train idea sounds great. Thanks for the restaurant recommendation