Berlin

Checkpoint Charlie is worth a five-minute walkaround. It has little resemblace to its former notorious self. There is a fake hut staffed by a couple of actors pretending to be border guards. The musuem is a private operation and I have not been inside so maybe it has more authenticity.

Is there another area of the city that would have more character, but still be a safe area to walk during the evening hours?

Yvonne, I stayed at Pension Peters in Berlin and would highly recommend it. The room was clean and comfortable, the staff were wonderful and there are some nice restaurants and a great Pub right around the Hotel. The Pension is in a great location between Savignyplatz and Bahnhof Zoo, which makes transportation very easy. The Original Berlin Walks tours leave from the area of Bahnhof Zoo, so if you're considering a walking tour, they're only a short walk from the Hotel. You might find it helpful to have a look at the Snapshot Berlin Guide, either in print or E-book version. There's LOTS of good information there on all the sights in Berlin, hotel and restaurant suggestions and information on the best methods for getting around the city. Happy travels!

Berlin Mitte is perfectly safe. The only downside is that because it sits very close to the center of government, hotel rates tend to be well above the city average.

I've stayed at Pension Peters and at Hotel Otto, both of which are reasonably priced and comfortable (Otto is a little more upscale, no breakfast). Both are also close to the Savignyplatz S-Bahn station (in what was West Berlin). It's fast and easy to get to the rest of the city on the S-Bahn. Both hotels are also near Bahnhof Zoo, a major transportation hub. I've always enjoyed hopping on buses from there and seeing where I end up. If you're looking for an educational and interesting private walking tour, check out Minnesota native Jeremy Minsberg (http://www.theberlinexpert.com/). Berlin is a vibrant, fascinating city. Enjoy!

The others are right, Checkpoint Charlie is not a very good place to stay. But I also disagree about staying in the former West sector of the city. The U-Bahn is a marvel in Berlin, but it is a very spread out city and with prices being the way they are in Berlin (cheaper than you might think!) there's not really too many reasons to stay in the West unless you're partial to it. There are many reasonable options in Mitte, specifically off Friedrichstrasse, Oranienburgstrasse, or Rosenthaler Platz, all within a short walking distance to Museuminsel and usually right on top of an U-Bahn or S-Bahn stop.
I have personally stayed at Arcotel Velvet on Oranienburgstrasse and recommend it; many others here really like the Circus Hotel, right at Rosenthaler Platz. Both locations are wonderful and the hotels get lots of praise.

Yvonne, the tourist attractions in Berlin are somewhat spread out, although there is a sort of "cluster" in the Mitte that are somewhat walkable. That said, I don't prefer the area around Checkpoint Charlie despite having stayed near it (right above it recently) twice - it's just too boring at night with no good restaurants or anything going on. But it's safe. It would help to know your budget. The Archotel John F is a nice mid-range hotel in the Mitte, close to Under Den Linden but also Checkpoint Charlie. Might work for you. My personal preference is to stay in Kreuzberg or Prenzlauerberg, but that's more for food/nightlife and less for sightseeing so I don't know if that would be a good choice for you. Don't overlook hotels near the main train station (Hauptbahnhof) - while not exactly a romantic area, there are good deals and it's very easy to get around from there.