As someone else mentioned, the trip would depend upon you and your wife's interests.
My wife and I have discussed Greece. Alternatively, a great romantic trip, with things to do and time to relax would be to rent an apartment in the Campania region of Italy. You could be near Sorrento.
There are many wonderful sites, but you can also just relax and enjoy the views.
http://www.italianvillasdirect.com/W...ItalySouth.htm