This Nature Reserve is one of the principal wetland areas in southern Europe. Covering 10.000 hectares it comprises an authentic labyrinth of dunes, water channels, swampland and beaches. Its location, between the neighbouring Doñana National Park and the Straits of Gibraltar means that it is a fundamental part of the migratory system of a multitude of seabirds, and indeed, it is classified as of international importance in this respect. In the channels, not only birds seek refuge, but also countless varieties of fish, molluscs and crustaceans. Its varied natural vegetation includes salicornia, used by the salters to roast the fish from the fish farms, giving it a totally unique flavour.

There is a whole network of trails criss-crossing the marshland and leading to spots of outstanding natural beauty: the Rio Arillo Trail, the Punta del Boqueron Trail and the Carrascon Trail. Bird-spotting is a particularly favourite pastime along these trails. The ever-changing colour of the various expanses of water is breathtaking and it is easy to appreciate the astute distribution of the fish farm channels, which allow the water to heat up and for some pre-evaporation to take place, before some is finally channelled off into the salt flats proper, to evaporate entirely.