The category was "Countries' Local Names". The answers were Polska, Nippon, Magyarország, Hellas, and Suomi (Poland, Japan, Hungary, Greece, and Finland).
I knew them all - though, in typical Jeopardy! fashion, I admit I wouldn't have been able to come up with Hungary's name had that been the way the category worked, and would have said Rzeczpospolita Polska for Poland. But it seems to me those were pretty simple for a Double Jeopardy round. And it seems to me that having "Hellas" be a Daily Double was symptomatic of the way the show's quest* for another ratings-inspiring multi-show champion has led them, ironically, in the other direction: the questions are so easy that challengers unseat champs on a regular basis.
* This quest may not in fact exist but quite a few of the people I know who watch think that's what's happening this year.