On the Tres Amigos-Río Arillo hiking 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 is found on the branch to the left of the car park, heading towards Playa de Camposoto, another is at the end of the path about 3 kilometres from the beginning. These first two observatories face the estuary of the old salt mine, therefore the waters that have been retained using gates that take advantage of the tidal cycles. In this area, flamingos, avocets, godwits and terns among many other bird species, are very common. There is a third observatory, near the second one which faces the Río Arillo channel, where at low tide we can see a multitude of small waders such as dunlins and plovers.

We are in an area of great ecological interest as it is 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 many 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, labyrinths of pipes, estuaries and walls, is the result of the use by man since ancient times of the marshes that lend 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 of the Bay of Cádiz, with more than 140 salt plains until the middle of the 20th century. We have been left a legacy of high ethnographic interest with the vestiges of the salt culture, including houses and buildings linked to salt mining, the salt mines themselves and the tidal mills such as the one in Río Arillo, one of the 19 that the bay was home to. With its twelve stones, the Río Arillo mill is the best example of this technology in the Bay of Cádiz and is included in the General Catalogue of Andalusian Historical Heritage.