The first city you build is your Capital. It is marked with a star (★) and has significant civic bonuses to other cities.
In some games, losing it can mean a defeat for you. In Sudden Death, the moment it is lost, you will lose. In many others, there is a timer, and when the timer times out, you lose the game.
Building the Senate in a city, which is not your capital, makes this city a capital. If built in a capital city, it does nothing other than its normal functions.
Unique Nation PowersEdit
The Persians can have 2 capital cities at the same time and both must be captured for the defeat timer to start.