The "Pateira of Fermentelos" or simply Pateira is a natural lagoon, located in the triangle of Agueda municipalities, Aveiro and Oliveira do Bairro, before the confluence of Cértima river, with Agueda river. It is surrounded by the parishes of Óis da Ribeira, Fermentelos , Espinhel and Requeixo. It is the largest natural lake in the Iberian Peninsula. It is a very rich area in fauna, flora and aquatic species, including several species of birds.