One of the nicest buildings in Piazza dei Cavalieri is the Palazzo dei Cavalieri, originally the knights' military training quarters, and today the Scuola Normale Superiore, an institue of higher education.
In the picture you can see the statue of the Grand Duke of Tuscany, Cosimo I de Medici, which stands in front of the Palazzo dei Cavalier.
Other remarkable buildings in this square are the Palazzo dell'Orologio (Clock's Palace) and the Church of Santo Stephano dei Cavalieri.