The innovative city culture of Florence was the crucible within which Renaissance ideas first caught fire. With its soaring cathedral dome and its classically-inspired palaces and piazzas, it is perhaps the finest single expression of a society that is still at its heart an urban one. For, as Brian Jeffrey Maxson reveals, it is above all the city-state - the walled commune which became the chief driver of European commerce, culture, banking and art - that is medieval Italy's enduring legacy to the present.