A serious amount of steps, I believe over 450. View are fantastic over the roof tops of Florence.
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.
Climb to the top to get one of the best views of the entire city. There's not much that's taller than this.