The Reserva Natural do Sapal de Castro Marim is a protected wetland that covers the salt pans, marshes, and mudflats behind the coast near Praia Verde and Castro Marim. It is one of the most important bird habitats in the eastern Algarve, hosting significant populations of flamingos, spoonbills, herons, egrets, and various wading birds year-round. During spring and autumn migration, the numbers swell considerably.
The reserve is free to enter and there are walking trails along the salt pan dykes that give good access to the habitat without disturbing it. Flamingos are visible almost any time of year, often in groups of several dozen birds feeding in the shallow pans. A small visitor centre near Castro Marim town provides information about the reserve and its wildlife. Binoculars help considerably — the birds are not shy but the flat landscape means distances can be deceiving.