Quite a steep climb, so be sure you're up to it first. Great view of the Duomo.
The Campanile, or tower, is almost 300 feet high, and it makes for almost a perfect complement to Brunelleschi's Duomo. The Campanile is called Campanile of Giotto, but while Giotto drew the plans, he died a year into the project. It was finished for another seventy years after Giotto's death.
314 steps to the top and well worth the climb - just be sure to bring some water and take a break when you reach the landings!
Come here, do the climb. At 274' tall, this gives you the classic view over Florence and the rooftops. Beautiful.
A serious amount of steps, I believe over 450. View are fantastic over the roof tops of Florence.