Trash said:
Exploring them was the biggest draw of the otherwise extremely mediocre game.
They certainly looked nice, but there were very few attention-grabbing areas or landmarks to check out. After you saw one street filled with shuffling plebs you'd seen them all. All that was left was to climb a building, sit on it, see another building that was kind of tall, say, "I want to go over there, now," jump down, and start climbing again.
There needs to be small interesting details in order for the cities to have life. You can capture the 'feel' of a city through aesthetics but none of that matters when you've saved the same peasant lady from oppressive guards 15 times in a row. Unique shops, characters, sporting events, conflicts, and quests are what AC needs IMHO.