Bagnaia is a little hamlet in the Municipality of Perugia, at 11 km of distance. At the end of the XIV century it was a castrum - castle, and seat of the administration vicar delegated by the City of Perugia. The absence of any documentation requesting money from the Municipality of Perugia, a common procedure for the adjacent hamlets, may signify that the castle had been built with the only resources of the community and this makes difficult a correct dating. The castle ward included a rich property of the Abbey of San Pietro in Perugia.In 1365, in the westward plain near Bagnaia, called Pian della Battaglia (Battle Plain), three thousands knights fought the battle between the British- Hungarian mercenaries of John Hawkwood, sent by the Pope to subdue Perugia, and the German mercenaries of Baumgarten, for the defence of the City. The British troops were defeated and imprisoned in San Mariano castle. In memory of the victory a church entitled to San Nicolò was built, today in ruins. In 1416, the Bagnaia castle was besieged by Braccio Fortebracci da Montone. During the Middle Ages the area belonged to Porta Santa Susanna and Porta Eburnea Districts.From the XVI century, when the hamlet was no more a defence fortress, the castle changed its appearance: doors and windows were opened in the walls.