Actually it's not as difficult as might seem at first. The most difficult ones to put are the initial buildings cos there are no reference points nearby. It took me 2 hours just to place the Temple of Jupiter and the Circus Maximus, and even there a lot of time was saved because I was doing both placings at the same time. But once this is done, placing the Curia nearby took 15 minutes, and everything after that will take even less time, considering the fact that I'll be placing many buildings at once, and so a lot of time will be saved on quitting/restarting RTW. In general, it's not as bad as you imagine, you can place the entire city in a day or two, if you put your mind to it.