Festivities of Plasencia de Jalón Activity · Plasencia de Jalón, Valdejalón, Zaragoza Image of Plasencia de Jalón, not of the place itself. Plasencia de Jalón, documented since 1125, celebrates its main fair on 7 September. It was a lordship of the counts of Luna and passed in 1429 to the Lanuza family; its church of San Juan Evangelista, with a Latin-cross plan and an octagonal dome over the crossing, dates from the 17th century. Photo: Diego Delso (CC BY-SA 4.0) What to see and do in Plasencia de Jalón