Laguna de Castillos

Comprising approximately 8,000 hectares, this lagoon is unique in that its connection with the ocean is a natural canal, the Valizas stream. It runs for 17 km and exhibits marked meanders, arcs of its primitive bed, with small islands in its tributaries. This creates a landscape of great beauty, with the added feature of the longest yearly connection with the ocean, with strong currents to and from the sea and frequent wind tides.


Another unique feature of this lagoon is the sandy strip around a large portion of its coast, with a natural forest dominated by coronillas (Scutia buxifolia) and ombú ((Phytolacca dioica). A significant part of the lagoon coastline is covered by reeds, which on the north coast are several hundred meters wide and form islands in the lagoon. (Source: Juca Gambarotta).

Laguna de Castillos was declared a refuge for wildlife by Decree 266 dated 1966, and in 2020 it was integrated into the National Protected Area System under the category “Protected Landscape”. This first stage of protection includes two tracts of public land, the body of water of the lagoon and the body of water of the Valizas stream, from the bridge over route 10 to the lagoon.


The area integrates the Bañados del Este y Franja Costera site, designated by the Ramsar Convention, an intergovernmental agreement to protect wetlands of international importance for the protection of wildlife. It is also part of the UNESCO Biosphere Reserve  Bañados del Este of the Man and the Biosphere Programme. This ‘Eastern Wetlands’ region comprises a complex of ecosystems of high biological diversity and rich wildlife, including the butia palm (Butia capitata) forest and the ombú woodland.


Decree N° 059/020 dated 14 February 2020, which provides the perimeter and classification of the natural protected area Laguna de Castillos, sets out the measures of protection for the area. (Source: Probides).

PH: Juca Gambarotta

A high diversity of fish is found here, especially noticeable for the mixture of fresh and salt water. Both saltwater and freshwater fish are captured by the community of fishermen located near the bridge over route 10.

Among them, we may mention bagre negro, el pejerrey y la tararira y entre las de agua salada la corvina blanca y el lenguado.

Other species with commercial value are the blue crab and the shrimp. The latter is growing in commercial relevance, and is extracted at the end of the summer and autumn. In the seasonal waterholes that border the fields adjacent to the lagoon there are at least 4 species of annual fish, among them Austrolebias viarius, endemic to a small area centered in Castillos.

15 species of amphibians, 36 mammals, 16 reptiles and 267 species of birds have been recorded in this lagoon, many of them of importance for conservation. This is also the case of the palma butiá which forms dense palmares in the area proposed for designation under SNAP.

To many, the great attraction in this lagoon is the ombú forest, but an indubitable complement to the traditional boat tour is the abundant birds that can be observed on the margins of the Arroyo Valizas. Black-necked swans are more easily viewed in the lagoon during the summer, when the marshes have less water or are dried out; but the coscoroba swans, while also more numerous in the summer, are easily seen all year round. The population of black-necked swans is between 1,000 and 1,400, but during the long drought of the year 2000 some 5,000 individuals were recorded. Coscoroba swans number between 300 and 700. However, the most abundant species is the cuervillo de cañada, when they congregate at their resting spots, and gallaretas.

Laguna Castillos plays a very important role as a refuge for birdlife, when tens of thousands of gallaretas are observed. During the 2015 drought, an estimated 40,000 were seen in the lagoon. Also, most of the species of ducks recorded in Uruguay have been observed here.

The lagoon and the ombú forest may be visited via three points:

Barra Grande: 099050631,
Guardia del Monte: 099872588

Monte Grande and DINAMA land (including a tour of the Valizas Canal): 099295177

Text: Juca Gambarotta