To understand Florence, you need to think of it in four stages of development. First: Florence the city founded as a Roman army camp. Studying a map of the city today around the Palazzo Vecchio, one can find the grid of the streets from the camp with its main avenue (or 'cardo' as the Romans called it) running north/south through this area. Second: Florence the medieval city grew around the old camp. The outer limits from this stage are marked by the medieval wall. Third: Florence the capital of the Renaissance, experienced a number of important urban interventions to make the city more livable.