Located in the south of the province of Huelva, at the convergence of the mouths of the Tinto and Odiel Rivers, the confluence of fresh and salt water has produced an area of tidal marshland known as the Odiel Marshes.

The system functions like an estuary, with both rivers depositing a large amount of nutrient-rich sediment at their mouths. These are the main food source for the birds that live in the Nature Area. Meanwhile, this constant supply of nutrients and the strength of the tides forms islands separated by long channels of water, such as the Islands of Enmedio, Saltés and Bacuta, to the south of the area. This salt-water environment determines the predominance of plant species resistant to high salt concentrations, known as halophyte plants. One example of these is salicornia or saltmeadow cordgrass, one of the basic elements of the ecology and landscape in a large part of the marshes.

Part of its ecological wealth stems from the variety of landscapes that make up this area. From tidal marshes to lakes such as Batán and Taraje, along with Espigón Beach and the forests of El Almendral, El Acebuchal and La Cascajera. It is unusual on account of its extreme flatness. This means you can enjoy the scent of saltpetre, the sea breeze and the spectacular arrival of hundreds of birds that come to this area of marshland to feed, and often also to nest in the safety of the surroundings.

One of the main areas is the Isle of Enmedio. It has the Nature Reserve designation because it is home to one of Europe's largest breeding grounds for spoonbills, which are an endangered species. These birds build their nests with mud and a range of plant material to make small platforms located in these marshland areas in the shelter of annual sea-blite and saltmeadow cordgrass plants. When the eggs hatch, the chicks are fed by both their parents, mother or father indistinctly. Furthermore, take a stroll in this Natural Area and you will be able to see grebes, cormorants, flamingos, diverse species of gull, as well as waders such as redshanks, stone curlews and black-winged stilts. This could also be an ideal place for a pleasant boat trip, to see all these elements from up close.

Salt production is one of the most interesting uses of natural resources in this area. The Bacuta Salt Pans are an example of traditional extraction, while the Aragonesas are more industrial. Besides this, pine nut collection, beekeeping, livestock rearing, fishing and shellfish collecting are the main traditional activities in this natural area.

The wealth of minerals, salt and fish in this area, along with its strategic geographical location, led to this region being colonised by a range of different cultures. The ancient city of Tartessos is believed to have been located here. There are remains of fish-salting basins from Roman times, and the Salthish archaeological site on the island of Saltés dates back to the Moors; this was a major city, capital of the taifal kingdom of the Bakrids in the 10th and 11th centuries. Finally, for some wonderful views of the estuary, take a walk around the old Riotinto company loading wharf, built to load minerals arriving by rail.