Laguna de Castillos was declared a Refuge for Fauna by decree 266 dated 1966, and was designated as a protected area in February 2020.
It covers approximately 8.000 hectares, and is part of the chain of coastal lagoons resulting from marine transgressions that took place during the Holocene. Unlike the rest of our coastal lagoons, Laguna de Castillos does not exhibit a sand barrier parallel to the coast but a canal (Arroyo Valizas). It is some 17km long and presents marked meanders, arches of its original bed, tributaries with a dendritic appearance and islands between them, which endows the area with a unique geography.