Region of Thessaly (14,037 sq km) occupies the east side of the Pindus watershed, extending south of Makedonia Region to the Aegean Sea. The region is well delineated by topographical boundaries. The Chasia and Kamvounia mountains lie to the north, the Mt. Olympus massif to the northeast. To the west lies the Pindus mountain range, to the southeast the coastal mountain of Ossa and Pelion. The Trikala and Larissa lowlands form a central plain which is surrounded by ring of mountains. Thessaly’s major river, the Pineios, flows eastward from the central Pindus Range emptying into the Thermic Gulf. Several tributaries of the Pineios flow through the region. Around 100 natural wetlands, with a total surface of 4977 ha, are spread out over the Thessaly territory including riverine systems, lagoons and coastal marshes. In addition, 540 artificial reservoirs (2870 ha) have been recorded in mountain and plain areas complementing the wealth of water resources for multiple human uses as well as in support of biodiversity. Both natural wetlands and artificial ones conceive a network that crosses the 15 Natura 2000 sites of the region.