Florence has the greatest collection of Renaissance art in the world, and a character list that reads like a Who's Who of the period's greatest artists and thinkers u Dante, Leonardo, Michaelangelo u not to mention the powerful families who financed their work - the Medici and the Strozzi. Evidence of their lasting influence abounds today, including the discovery of a Leonardo fresco beneath a painting by Vasari, and the unearthing of Michaelangelo's plans for a church facade. The city's challenge today is to manage the resultant tourist hordes; a new entrance to an enlarged Uffizi should double tourist numbers to the gallery, while a tramline is intended to reduce the city's traffic.