Part of the reason you can walk across the city in this time is because it is really walkable. I'm from the Midwest - Trondheim is the biggest city I've lived in but more walkable than any of them. I'll add that the "across the entire city in less than an hour" isn't as true as it once was, especially when you consider that places like Klæbu are part of the city now and the population has grown. Byåsen would take me over an hour to walk to.

Den Gode Nabo is still about, but its been years since I've been there :)