This is inspired by GovernorSimulus' maximum population quest, but instead of that, I'll focus on getting 12k population in Old Kingdom period.
My personal rules on this quest will be:
* Very hard difficulty
* 12,000 population
* 100 prosperity rating
* All houses are residences or better
* All roads are connected, except entertainment venue
* All schools, libraries, mortuaries and senet houses are well supplied.
* Personal funds only used for kingdom rating
* Smooth population census - no aging problem
* Final city should runs with minimal intervention
Managed to get 10 palatial estates, 15 stately manors and 102 common residences in 4 housing blocks, squeezed tightly on half the map. That way, all people coming to the city can look at the entire city from across the lake, cloaked behind golden farms and lust desert woods.
On is the only city selling meats and papyrus. Roughly 3 trips a year means the maximum goods from On would be 4,800. So the challenge here is to get 10 palatial estate while maintaining all houses being residences or better at 12k population.
A form of improved Afterburner's flexi-block is devised to the purpose, reducing the number of housing block to 4. With Oracle of Thoth, 4 schools and 2 libraries write away 2,688 papyrus a year. 10 palatial estates eat 2,000 fine meats a year. In total, annual papyrus and meat consumption is 4,688, just below the 4,800 limit.
Since a slightest delay to On's merchant would lower the import limit, I keep the shortest route for them as well as building storage yard right next to it. Other merchants will go sightseeing with the longer route.