Holiday gift for boyfriends 25th birthday?

Hi hi. My partners turning 25th in November ( I know I know long way ahead) and Ive been wanting to give him something he will remember. Now, he enjoys many things but we both absolutely love travelling and spending time with each other, its not something materialistic gifts would replace. I have been looking around for holidays and countries but not entirely sure where would be better. Preferably outside the EU. Any recommendations from any of you that have gone anywhere as a "romantic" trip?

Budget is £1500 for both but going over that would not be an issue.