Frescoes painted by the Umbrian Bernardino di betto, called Pinturicchio, probably based on designs by Raphael. The frescoes tell the story of the life of Siena's favourite son, cardinal Enea Silvio Piccolomini, who eventually became Pope Pius II. He was the uncle of cardinal Francesco Piccolomini Todeschini (then archbishop of Siena and the future pope Pius III), who commissioned this library in 1492 as a repository of the books and the manuscript collection of his uncle. The ceiling is covered with painted panels of mythological subjects. They were executed between 1502 and 1503 by Pinturicchio and his assistants.