Slovenia!
I did a Gate 1 week-long tour to Slovenia and had a nice time. Our guide Marina was knowledgable, funny, and super smart. The hotel was nice and centrally located, our daily tours were always a lot of fun and even though our group had around 31 people, it didn't feel crowded. Everyone we spoke with on our tour had already been on 4, 10, or even 60 prior Gate 1 trips. That tells you all you need to know.