First, let's place Confucius in time. He lived during the Eastern Zhou dynasty, specifically during the period called the "Spring and Autumn Period." Remember, Confucius lived several centuries before the First Emperor, and there were many drastic changes in Chinese society during then.

The Cambridge History of Ancient China is a good reference for this. Professor von Faulkenhausen writes (p.453-463) that society during the early Zhou period was dominated by kinship elite lineages at walled settlements 城 with wooden buildings on rammed-earth foundations. He argues that most people probably lived in thatched huts outside those settlements, unlike the elite. The "city" would have major walls with gates, made of rammed-earth. Some ritual areas would be outside of the city for sacrifices or religious rites. But ultimately, early Zhou settlements can't really be called cities per se (least not in our modern conception of the term), certainly not in the mold of Chang'an or Luoyang centuries later.

During the later Zhou period of the Warring States (after Confucius's death) societies changed dramatically, with cities becoming political and economic as well as ritual centers. Wu Hung writes about this in the same volume, noting that during the Warring States period cities became more important since there were fewer states left and shoring up your defenses was integral to surviving. Furthermore, economic activity becomes very prominent in those state capitals, and the cities pretty much just grew more haphazardly without the ritual orderliness of the Western Zhou era. Linzi, the capital of Chu, was said to have 70,000 households and 210,000 adult males (p. 655) and it was so crowded that one would constantly rub shoulders with others while traveling in the city.