Tucked into the 1469 Florentine Renaissance-style Palazzo Piccolomini off the southeast corner of the Campo, this state archive displays such historic documents as Boccaccio’s will and Jacopo della Quercia’s contract for designing the Fonte Gaia fountain. The intriguing “Tavolette di Biccherna” is a remarkable set of wooden covers made in 1258 for the city’s account books; they’re painted with religious scenes, vignettes of daily working life, and important events in Siena’s history. Note the Piccolomini family coat of arms above the palace entrance; the papal tiara in the crest refers to the family’s most illustrious member, Pope Pius II, who served from 1458 to 1464. You’ll see portraits of him in the Duomo’s Libreria Piccolomini; he was also known for designing the town of Pienza, the first planned city in Europe.