La Vaca Vieja Activity · Molinos de Duero, Pinares, Soria Image of Molinos de Duero, not of the place itself. The village's carnival is celebrated with the Vaca Vieja, and the festive calendar is completed by the may, the feast of Santiago Apóstol at the end of July, with a medieval market, and San Martín on 11 November. Photo: Wamba Wambez (CC BY-SA 3.0) What to see and do in Molinos de Duero