I tried to achieve a city as big as possible, and this city can reach 40k pop. However, this game has a sprite limit aka DATA LIMIT. Whenever I try to increase the population over 30k, there are troubles with walkers. For example, the vendor's walkers will disappear sometimes, or the sculpture studio won't produce anything even if it is near a storage full of bronze. The game is about 20 years old, but I hope the developers will remove the limit in new patch.
P/S: I tried the house block model called Plebus' Trojan War Block with optimization which yield 40 common houses in minimum space of 24x15.
Update: I updated an upgrade city with 42,120 people. I made some changes to reduce the number of walkers like reducing agricultural area, importing as many essential goods as possible, etc. There's a minor issue with the occasional fire near Hephaestus and Aphrodite's battleground.
Food support: 45,072
Stored food for 16-17 months
160 soldiers in 20 companies
Balance: 7 mil.
Net worth: 50k per year
Employed Workforce: 14,301
Sanctuaries: Apollo, Aphrodite, Ares, and Athena.