Corsica is actually a pretty interesting port stop. I am assuming you will be in Ajaccio. You can walk from the tender pier into the smallish city where you will find some nice cafes, and a few shops along the main street. If you like beaches, you can simply walk towards your left (from the center of town) and after a few blocks you will come to a nice sandy beach which is fine for sun bathing or swimming. Other than the beach, Ajaccio does not offer much for tourists. The island is actually a pretty big place with some very scenic places. On one ocassion we decided to take a tour to the "Calanches" (we seldom take tours) and actually enjoyed the bus ride across the island. We usually consider this port a nice restful day (not a bad thing on many Med cruises).