The USA has pockets of them....LA, Austin.....etc.....but Sweden has the most consistent ones IMO.... DD
I have family there. Make sure to check out the cathedral if you visit. For old-town style check out Heidelberg, or Lubeck. I've been all over germany and really enjoyed those two spots from a "old town charm" perspective. If you can, take a side trip to Dresden. Yeah, the city is, of course, rather moden - like most formerly-blown-to-smithereens german towns, but the landscape is spectacular (florence on the elbe) and the newly rebuilt Frauenkirche is amazing. I'm also partial to northern germany (Schleswig-Holstein) since that's where most of my family is from. Kieler Woche is a fun time (although not while you're going to be around). I'm going to Germany myself in two weeks. With two children under age two. Pray for me.
Or Russia / Ukraine. To the OP. I'd recommend going to Heidelberg. Great city and its about an hour drive down from Frankfurt airport. I spent 3 months there working. Its a tourist/university city. Many of the people there speak english. There is a nice river running through the town, a cool castle you can tour, and many breweries with some good beer. Its also one of the few cities that wasnt' bombed during the war so some of the older buildings and history are still intact.
It is in my territory, I may have to go down there in...uh...February and meet with game developers. They were my 2nd choice behind Sweden. DD
Even if you're traveling as a single guy, I highly recommend renting one of these: We're not going to Moscow. It's Czechoslovakia. It's like going into Wisconsin.
I havent been much out of the US, other than Canada and Mexico and couple other central america countries. But I got to visit Brussels for work for 2 weeks a year ago, and it was amazing. If you have time, spend a day or two there, beautiful city. The gf and I are planning on going to Europe in a year and hit up Octoberfest in Germany, as well as a few other counties (Italy without a doubt).