Bahariya, right before completion. After the sun temple finishes, victory is declared with these results:
Level: Very Hard
Personal funds, debt, and the "rescue" gift were not used. However, before starting, I checked that a trade route supplying beer or barley would become available. And I replayed the last 18 months to get more tax money (without tax rate "tricks", of course), since the perimeter wall and towers cost a fortune. Even so, there was barely enough money to finish the defenses.
The final city has these points of interest:
* A double wall, with gatehouses and frequent towers, surrounds the city.
* All original trees exist (although many are cut for wood).
* The Kingdom Road exists in its original location.
* All roads are connected, but caravans stay on the Kingdom Road.
* 2 foods and 7 other goods are imported (not counting sandstone).
* 7 goods are exported (6 made from imports), but some in small amounts.
* Each import has a trading storage yard, usually shared with an export.
* Fire protection is better than would be needed at a lower difficulty.
* The libraries, school, and mortuary are kept supplied.
* Every house is a common residence, fancy residence, or spacious manor.
* The festival square has regular traffic.
* The city center includes all "nice" structures. (I like that the sun temple's fore temple opens onto the festival square.)
The city should be stable for many years without intervention except to defeat invasions. (To run for more than 5 extra years, immediately set sandstone to stockpiling.) All towers in the perimeter wall have guards in 4 months, and goods in storage yards reach typical levels in a few more, but it takes about 21 months for the population to stabilize at 4572. Funds increase by over 10000 Db in each extra year.
The "training tower" near the recruiter (next to Dune Nature Park) was built last, to ensure that all perimeter towers get guards. (Occasionally, the last tower built doesn't get a guard.)