If you're considering Europe, you might want to start with Ireland. I've been twice, and I've known many others who've gone, and it's universally considered a great time. The people will treat you like an honored guest and the scenery, culture, and history guarantee you will find plenty to do no matter what you're into. On my last trip, I was invited to a wedding reception in Holy Cross, and when they found out we were Americans, they wouldn't stop buying us rounds and introducing us to ever more friends and relatives. The reception went on for three days and we got to watch a local Gaelic football match between two rival towns where half the wedding party played on one side or the other. Definitely a memory I'll cherish forever.
If you're more adventurous and self-reliant, then go to Italy. Except for Rome, it's very clean, safe, there's loads to do and see, and the people are warm and helpful to travelers. The food, wine, and art will blow you away, second to none, anywhere.