Soastus: ancient Greek name of the river Swat in Pakistan.
The valley of the Swat, the ancient Soastus, belongs to the most fertile areas of modern Pakistan. There are pine forests and lush green plains, and it comes as no surprise that the ancient Indians called it Udyana, 'the garden'.
Alexander the Great conquered the southern part of it in the spring of 326. After the capture of Massaga, he entered the Swat valley near modern Chakdarra. His marshals captured the two fortresses at Bazira and Ora.
The photos below show the river near Barikot (Bazira), the river near Chakdarra, and the river together with the Hindu Kush mountains. To the right is the beginning of the Shang-La pass, which is the shortest route to the river Indus, where Alexander captured the Aornus rock.