The Lagoon of Aveiro is the result of the retreat of the sea, with the formation of coastal strings that, from the 16th century onwards, formed a lagoon that constitutes one of the most important and beautiful geographical features of the Portuguese coast.

In total, the entire mouth covers eleven thousand hectares, of which six thousand are permanently flooded, unfolds in four important channels branched in estuaries that surround numerous islands and islets. It flows into the rivers Vouga, Antuã, Boco and Fontão, having as its only communication with the sea a channel that cuts the coastal cord between Barra and São Jacinto, allowing access to the port of Aveiro by large draft vessels.

Rich in fish and water birds, it has great water levels, places of choice for the practice of all water sports. In addition, even though it has been losing its importance in the Aveiro economy from year to year, salt production, using ancient techniques, is still one of the most characteristic traditional activities in the city of Aveiro.