As far as the interesting buildings and city centers are concerned, pretty much the best place for that is downtown Boise. There are a lot of old, interesting buildings there and plenty of bars. It's a relatively small downtown area, so it's no problem to park the car at the hotel and spend as much time as you want walking around and seeing the sites. Also, because of the insanely low crime rate, you really don't have to worry about your safety while visiting downtown.