Located in the southernmost Chianti Classico zone, San Giusto a Rentennano began life as a medieval monastery of Cistercian nuns and was called San Giusto alle Monache ("of the Nuns"). The oldest part of it was built in the early 13th century and today some portions of the ancient fortification still stand, including its crenellated battlements, massive barbican walls and underground vaults, which are used today as the their ageing cellars. In 1957, it was inherited by Enrico Martini di Cigala and in 1992, it passed to his children, who now manage the property. This impressive estate is comprised of 160 hectares (certified organic in 2009) and has a microclimate that is characterized by considerable day and night temperature differences, enabling the grapes to take their time to ripen. The estate produces two Chianti Classicos as well as IGTs, including Percarlo, a 100% Sangiovese wine from their finest and lowest yielding vines.