On the Tres Amigos-Río Arillo trail there are three observatories that allow us to get closer to one of the areas of greatest ornithological interest in the Bahía de Cádiz Natural Park.

The first observatory is found on the branch that runs to the left of the car park, heading towards Camposoto beach. This and another observatory at the end of the path, about 3 kilometres from the beginning, face the estuary of the old salt mine. The waters here have been retained by the use of gates taking advantage of the tidal cycles. In this area, it's common to see flamingos, avocets, godwits and terns, among many other bird species. There is a third observatory, near the second, which faces towards the Arillo river channel, where at low tide we can see a multitude of small waders such as dunlins and plovers.

We are in an area of high ecological interest, one of the most important coastal wetlands for the reproduction of aquatic birds in Europe, a priority area for the nesting, resting and feeding of numerous aquatic birds and a fundamental place for the reproduction and fry of numerous species of fish and invertebrates.

The landscape associated with the salt flats, with its labyrinths of channels, estuaries and walls, is the result of the use made by man since ancient times of the marshes that give uniqueness to the landscape and faithfully reflect the culture and economy of the bay. The Cadiz salt industry was one of the most important and emblematic economic activities in the Bay of Cádiz, with more than 140 salt plains until the mid-twentieth century. These have left us a legacy of high ethnographic interest as it houses the last vestiges of the salt mining culture, with houses and buildings linked to salt mining, the salt mines themselves and the tidal mills such as the one on the river Arillo (one of the 19 located in the bay) which has twelve stones and is the best example of this technology, it is also included in the General Catalog of Andalusian Historical Heritage.

It is not advisable to do this hiking trail in summer and it is recommended that you take binoculars or a telescope to be able to observe the many birds that can be found along the route.