As far as I can remember, I had never built a city of more than 20000 until now. In fact, another upload, Tingis, might well be my second largest city, I am not really sure. But when it comes down to stable cities, with good housing quality, then it is for sure.
One of the biggest challenges was logistics. I have more than 30 granaries, and a lot of warehouses getting food and goods all over the map. I had to keep in mind where to build granaries and markets, as I wanted to prevent certain houses from getting foods I did not decide to give them. It is one of the quirks of the game, that players can't decide what a market will or won't buy. Pharaoh has it, for example (along with roadblocks). But Pharaoh has been developed after C3, am I right?
I developed this city with one great oversight. I did not realize, how small the walker sprite limit is! I had massive devolutions, and I was forced to kill almost all of my soldiers, and many entertainment schools, to make room for more development. Luckily, there was no real invasion in the whole gaming time (28 years, +5), so I was OK with one javelin cohort. I also aimed for 100 culture, but couldn't afford to build enough schools.
The city could have gotten even bigger, if I did not reach the limit. there is room for 2 more blocks, fed on fish, and I did not utilize all of the farmland effectively.