Sorry, I assumed you were American. In that case, I don't think it's all that rare not being able to name two cities in a state — IME, a lot of capital cities are well known, but not necessarily second cities, etc. I think the capitals are often presented alongside their state as pairs, so phrases like "Detroit, Michigan" just stick in the mind. I also probably know Detroit, Michigan from either Eminem or Motown. Flint, Michigan is definitely more obscure — I know that one from Michael Moore. I do have a bit of a love for Geography, place names, and US states in particular.