The Thessalian plain is the second bigest valley in Greece, and the dominant geographical feature of the Greek region of Thessaly.
The valley is watered mainly by the Pineios River and is surrounded by mountains (predominantly the Pindus mountain range).
Through antiquity, the plain was extremely fertile, fact which made Thessaly one of the very few areas that could field large numbers of cavalry. The Thessalian cavalry was an important component in the Macedonian army of Philip II and his son Alexander the Great.
Philip II had as a life-goal to conquer entire Greece under his banners. The only army he was not risking an open war upon were the Thessalians; and that was due to their cavalry. The Thessalian cavalry was the most fearsome and well-equiped in the whole Greek territory. So Philip, instead of declaring war upon the Thessalians, took advantage of his diplomatic skills and formed an alliance with the generals of the Thessalian cavalry. Apart from that, he moved further a step and offerd his daughter as a bride to the Genaral of Arms of the Thessalian cavalry. After the marriage, the daughter of Philil took the name of Thessaloniki, which is a combined word; it means victory over the Thessalians (Thessaly (from the plain), and niki which translates as victory). A victory not through the battlefield, but a victory nonetheless.