The Mondego river has its spring on the Estrela mountain, municipality of Gouveia, at an altitude of 1425 metres. Between the spring and the mouth, the Mondego flows along around 220 kilometres. Its banks, between Coimbra and Figueira da Foz, are the most fertile lands in Portugal.

Located near Quiaios, the lagoon is roundish, with an approximate diametre of 600 metres, and it is surrounded by a lovely tree area. It has little depth and that explain its dense vegetation, typical of swamp areas. In this place, a havem for aquatic birds, there are bird observatories and a Centre of Environmental Education.