Flocculencio
Donor
Umm.... Jakarta ?
I mean, it is even bigger than Singapore...![]()
It's location isn't nearly as good though.
As David says the problem is for a city-state to survive it needs a very special set of circumstances. It needs to be culturally different enough from it's neighbours to prevent absorption due to, it needs to be economically significant enough to have a viable national economy without any natural resources and it needs to have some way of being protected from bigger neighbours during the start of it's development.
Singapore had all these- majority Chinese population in a Malay region, complete dominance over the second busiest shipping route in the world and semi-separate historical development from Malaya as a British Crown Colony.