OT - Size of medieval capitals

[narf poit chez BOOM]

So, what level of organization would be nessasary for a 100k city?

I'm thinking, a duke just for the city, a council of lower nobles, a merchants/guild council of some sort, the obligatory wizard's guild, since this is a fantasy world, a guard organized around the city's sections, the nobles and rich merchants would no doubt hire additional guards for their section. And the duke would have his own guard, commanded, no doubt, by a minor noble. And, since this is the capital, the king would have his guard and the army.

I'm using European terms because I'm familiar with them, but if this city is more believable as a middle-easternish city, if someone would provide titles and a breakdown...