Regional Capital ???
Italy is divided administratively into Regions - the equivalent (though with differences in degree of autonomy etc) of counties in Britain or states in the US. Each region has its administrative centre in one main town, and the literal translation of the name for this town would the regional capital. eg Milan is the regional capital of Lombardy.
But capital sounds wrong to me used at a below-national level. The British equivalent is County Town - but county is so specifically british that it sounds wrong in an Italian context.
What's the equivalent in the States? Do you talk about a State capital or is there another term? How would you translate the idea when talking about countries with different administrative systems - in Japan for instance with the system of prefectures?