It went from being the biggest city in the world, capital of empires, to an important city, to a city, to being so unimportant that it seems it was just abandoned one day, what happened?
https://www.reddit.com/r/AskHistorians/comments/w8dy4/how_did_certain_ancient_cities_become_abandoned/?st=jjnxa9ho&sh=d85e7b24
Old post by /u/daeres talks a bit about it