I don't think a city of more than 100,000 would be possible without a substantial amount of civil management.
Deciding with bits are for streets and which bits are for buildings needs an arbiter of som sort for starters.
If a place had a sewer it probably had a government.
Sometimes I like to recall that somewhere in Tenochtitlan there must have been some Aztec administrator doing a job like making sure the road signs are repainted every few years.
