Fair of l'Oli del Montsià Activity · Ulldecona, Montsià, Tarragona Image of Ulldecona, not of the place itself. The Fira de l'Oli del Montsià is held in Ulldecona, a district where the Olivera Farga de l'Arion grows, a thousand-year-old olive tree from which oil is extracted from centuries-old trees. Photo: Jordi Roqué (CC BY-SA 3.0) What to see and do in Ulldecona