The first area is the Gulf of Kalloni, which includes the entire marine area of the Gulf, as well as a large number of terrestrial wetlands (salt marshes of Kalloni and Polichnitos, streams of Tsiknias, Vouvaris, Mylopotamos, Ennia Kamares, Potamia, Messa lagoon, etc. .). The area of 18,311.18 ha includes sensitive ecosystems (stagnant waters, rivers, estuaries, muddy or sandy lagoons, marine areas, salt steppes, etc.).
Bird species that are endangered and/or unusual for Greece and Europe nest or pass through the area. Examples include: coots, avocets, petrels, tawny geese, white storks, pink flamingos, cormorants, etc. The vegetation is also important with the presence of the Tracheia Pefki forest and the numerous burla and sedges that surround the wetlands and the bay.