The valley between Incisa and Arezzo contains accumulations of fossil bones of the deer, elephant, rhinoceros, mastodon, hippopotamus, bear, tiger, and more.
The Arno, which has its source in the Monte Falterona, one of the most elevated summits of the main chain of the Tuscan Apennines, flows nearly south till in the neighborhood of Arezzo it turns abruptly north-west, and pursues that course as far as Pontassieve, where it again makes a sudden bend to the west, and pursues a westerly course thence to the sea, passing through Florence and Pisa.
Gregory was on his way to Rome to crown Rudolph and send him out on a great crusade in company with the kings of England, France, Aragon and Sicily, when he died at Arezzo on the 10th of January 1276.
He has been honoured as a saint by the inhabitants of Arezzo and Piacenza.
The Sienese government conceived hopes of gaining possession of the city of Arezzo, which was first occupied by Durazzo's men, and then by Enguerrand de Coucy for Louis of Anjou; but while the Sienese were nourishing dreams of conquest the French general unexpectedly sold the city to the Florentines, whose negotiations had been conducted with marvellous ability and despatch (1384)..