"We are in the same city thirty years later."
Translation:Siamo nella stessa città trent'anni dopo.
https://onlineitalianclub.com/free-italian-exercises-and-resources/italian-grammar/a-o-in-a-or-in/ Here is an explanation of the rule. Basically, you are correct, in that 'a' is used for cities. However, for the non-specific 'city', they use 'in.'
Yes and I'm afraid there are many more examples of repetition to the point of boredom on DL. I've done "these architects are good but not original" several times today also on many previous days, and ditto for "The questions are still numerous". Idea seems to be that eventually you will learn and understand but i really don't have occasions when i repeatedly have numerous questions or want to talk about good/original architects - except about my son who is one in London! Oh dear, struggle on