I have had the same thing, years of dreaming about a city. Any new dreams that I have of this place attest to what I remember about it from other dreams. I can drive (in my dream) on the streets and now which road will take me to another part of the city, remembering where stores, buildings, parks, etc are from earlier dreams. It becomes even more surreal than dreams usually are, because of the intensity of this city.
I was reading a book called The Dreaming Universe by a physicist turned metaphysicist: Fred Alan Wolfe. In this book he discussed having the same types of dreams. Through research and talking with psychologists that work on consciousness and dreaming, he said that it 'could' be a whole 'nother life. I am not saying one of those multi-dimensional 'lives' that we are subject to in syfy movies, but an internal life. I guess, kind of like that online reality: second life, but within.
I am not sure that this would help, but if anything, you are not alone.
As far as underlying meaning, there are too many different types of dreams; the ones that are so out there that there really is no way to determine what it means, the ones where you are astro-traveling (which may actually apply here), and the ones that are, indeed, telling you something about some aspect of your waking life that you either need to take care of, be aware of, or to solve a problem in your life. Like the previous commenter said, analyze how you feel within these dreams, and that should give you a first step to understanding it. Unfortunately, you cannot go by dream books, as they only give symbolism to one particular aspect of a dream, not what all aspects of a dream mean in relation to each other.
For me, when I am driving, walking, or just living in my 'dream' city, I feel like I do on a day to day basis. Good luck!