Thessaly (Thessalia) occupies the east side of the Pindus watershed, extending south of Macedonia to the Aegean Sea. The northern tier of Thessaly is defined by a generally southwestnortheast spur of the Pindus Range that includes Mt. Olympus, close to the Macedonian border. Within that broken spur of mountains are several basins and river valleys. The easternmost extremity of the spur extends southeastward from Mt. Olympus along the Aegean coast, terminating in the Magnisia Peninsula that envelops the Gulf of Pagasai (also called the Gulf of Volos), and forms an inlet of the Aegean Sea. According to legend, Jason and the Argonauts launched their search for the Golden Fleece from that peninsula. Thessaly's major river, the Pineios, flows eastward from the central Pindus Range just south of the spur, emptying into the Gulf of Thermaikos.
The Pineios River flows through the northern edge of the most important topographical feature in Thessaly, the central plains. The Pineios has several tributaries that originate in a delta configuration that encompasses the entire plain to the south of the main river. The alluvial soils of the Pinios Basin and its tributaries make Thessaly a vital agricultural area, particularly for the production of grain, cattle, and sheep. Modernization of agricultural practices in the mid-twentieth century has controlled the chronic flooding that had restricted agricultural expansion and diversification in the low-lying plains. Thessaly is the leading cattle-raising area of Greece, and Vlach shepherds (of Romanian origin) shift large flocks of sheep and goats seasonally between higher and lower elevations.
The population center of Thessaly is the Greater Volos metropolis, a shipping center combining the cities of Volos and Nea Ionia with six smaller towns at the northern end of the Gulf of Pagasai. The nearly landlocked gulf provides a natural harbor at Volos for shipping the agricultural products from the plains just to the west and chromium from the mountains of Thessaly. The Northern Sporades (Vorioi Sporades) archipelago, administered by Thessaly's Magnisia Prefecture, forms a series of islands, three of which are inhabited, extending eastward into the Aegean Sea from the Magnisia Peninsula.
Thessaly never had an independent existence. It was fragmented and isolated from the main political developments of the classical period to the south, then it was occupied by the Macedonians and Romans, who were followed by a variety of tribes and peoples until the Ottoman Turks took control in 1393. The Ottoman Empire ceded most of Thessaly to Greece in 1881, the remainder in 1913.