Where should I vacation?

I’ll likely be taking a two-week vacation in December with my girlfriend, and we’re looking for a relaxing place to go that has plenty of nature and culture/history. I’ve been to Costa Rica before and am thinking of someplace like that. Right now we’re focusing on the Americas or Europe, but I don’t know how cold Europe would be in December. I’ve briefly looked at some of the Caribbean islands, and while I’m sure they are relaxing I don’t know if they have the natural variety that Costa Rica did - they seem all beaches, beaches, beaches. I’ve never been there, though, so I’m anxious to hear your experiences.

Where did you take your most relaxing vacation?