Trier is a very nice place to stay, I'm from Italy but I go often there, and I'm usually staying in the Warsbergerhof, in the city center. I think very few peole in Italy have ever heard about this city and know where it exactly lies, anyway I would raccomend you:
1)Bernkastel Kues, not far from Trier, along the Mosell river, famous for its wine and the small cozy old town.
2)Luxembourg city
3)Koblenz, north from Trier and along Mosell river
4)Haidelberg
5)a 'must see' in the region is "Burg Eltz" along the Mosell river: that's one of the best kept real and original medioeval castle, but I'm afraid it opens only from April
6)Further north there is the city of Cologne, famous for it's cathedral, and some museums
7)Frankfurt, not the nicest city in Germany, but modern and with many museums as well.
8)Mainz, close to Frankfurt, a nice city.