This valley is an inland province of Tuscany, stretching from north to south, its length, from the southern slopes of the Casentino above Arezzo, to the southern end of the Lake of Chiusi, some forty miles, and its greatest breadth between the suburbs of Cortona and the Poggia di Sta. Cecilia, where a chain of hills descends along the Sienese valley of Ombrone, about five-and-twenty miles. The Arno, coming from the Casentino, touches the north-western end of this valley, where, instead of pursuing a southward course seemingly prescribed by the nature of the ground, it ‘contemptuously turns its back,’ according to the poet’s expression,[258] on the town of Arezzo, and by a sharp turn, created possibly in old times by an artificial cutting, takes a direction almost parallel to its earlier one and flows towards Florence in the north-westerly direction. At a small distance west of Arezzo it unites with the principal Tuscan branch of the river, which gives its name to the valley watered by it along its whole length, the Chiana or Clanis of the ancients, the original form of which is still an unsolved riddle, for it presents the singular appearance of its course and falls being divided between two larger streams, the Tiber and the Arno, to both of which it bears its waters, the drainage of the flat valley being now facilitated by hydraulic works. It is these works which have entirely altered the appearance of this valley in the present time, and created a flourishing fertile land where, throughout the Middle Ages, the miasma prevailed so terribly that the poet was reminded of its misery in his wanderings through the place of punishment for the makers of discord.[259] When we view the wide plain from the loftily situated Cortona, the horizon of which is bounded by a chain of hills, above which on the south rise the volcanic peak of Radicofani and the immense trachyte mass of Montamiata, a splendidly green and excellently cultivated fertile land lies before us. There are numerous hamlets mostly elevated on the western hills, at the southern end, where two small lakes seem to announce the neighbourhood of the greater Trasimene—Chiusi, Chianciano, Montepulciano, Torrita, Asinalunga, Fojano, Lucignano, Marciano, Monte San Savino. Three states join here: the State of the Church, with its province Umbria; the land of Siena, with the valleys of Orcia and Ombrone; and the Florentine territory, to which by far the greater part of the Val di Chiana belonged. From the most ancient times this Val di Chiana has always been chosen as a battle-field, on account of its situation and uncertain boundary, as well as on account of level suitable for military operations. About the middle of the fifteenth century, in the Neapolitan war with King Alfonso, this place was celebrated, as also a century later, when Siena fell in the heroic defence of her independence.