Established in 1975, this nature reserve is mainland Portugal’s oldest, covering 20 sq km of marshland and salt pans bordering the Rio Guadiana. Winter visitors include greater flamingos, spoonbills and Caspian terns; in spring it’s busy with white storks. September is the best time to see European chameleons, when they descend from the trees to lay their eggs in the conifer woodlands.
Walking trails with interpretive signs fan out from the park's headquarters, located 1.8km south of Castro Marim.