Just got a sized 60 city as Assyria on Emperor level difficulty, no mods, all dlc when I won (turn 448). Played to turn 500 and managed to reach 64. I had multiple 40s and 30s as well. How? Got the following: Temple of Artemis, hanging gardens, religion was totally oriented to food, freedom allowed my specialists to consume 50% food, and my empire was quite tall pretty much the whole game, which allowed me to stay happy. I could've gone bigger, had I made a concerted attempt to not lose my religion and had I used many internal trade routes. Location actually wasn't a huge factor, I had a good start location but nothing crazy in terms of food.