The site of <a class="linkToPlace" target="_blank" href="/place?placename=Byzantium&groupId=415&placeId=767">Byzantium</a> is as regards the sea more favourable security and prosperity than that of any other city in the world known to us, but as regards the land it is most disadvantageous in both respects.
For, as concerning the sea, it completely blocks the mouth of the <a class="linkToPlace" target="_blank" href="/place?placename=Pontus&groupId=910&placeId=1634">Pontus</a> in such a manner that no one can sail in or out without the consent of the Byzantines.
So that they have complete control over the supply of all those many products furnished by the <a class="linkToPlace" target="_blank" href="/place?placename=Pontus&groupId=910&placeId=1634">Pontus</a> which men in general require in their daily life.
For as regards necessities it is an undisputed fact that most plentiful supplies and best qualities of cattle and slaves reach us from the countries lying round the <a class="linkToPlace" target="_blank" href="/place?placename=Pontus&groupId=910&placeId=1634">Pontus</a>, while among luxuries the same countries furnish us with abundance of honey, wax, and preserved fish,
while of the superfluous produce of our countries they take olive-oil and every kind of wine. As for corn there is a give-and-take, they sometimes supplying us when we require it and sometimes importing it from us.
The Greeks, then, would entirely lose all this commerce or it would be quite unprofitable to them, if the Byzantines were disposed to be deliberately unfriendly to them, and had made common cause formerly with the Gauls and more especially at present with the Thracians, or if they had abandoned the place altogether.
For, owing to the narrowness of the strait and the numbers of the barbarians on its banks, it would evidently be impossible for our ships to sail into the <a class="linkToPlace" target="_blank" href="/place?placename=Pontus&groupId=910&placeId=1634">Pontus</a>. Though perhaps the Byzantines themselves are the people who derive most financial benefit from the situation of their town, since they can readily export all their superfluous produce and import whatever they require on advantageous terms and without any danger or hardship, yet, as I said, they are of great service to other peoples.
Therefore, as being the common benefactors of all, they naturally not only should meet with gratitude from the Greeks, but with general support when they are exposed to peril from the barbarians.
Now since the majority of people are unacquainted with the peculiar advantages of this site, as it lies somewhat outside those parts of the world which are generally visited,
and as we all wish to have information about such matters, if possible visiting personally places so peculiar and interesting, but if this be out of our power, acquiring impressions and ideas of them as near the truth as possible, I had better state the facts of the case and explain what is the cause of the singular prosperity of this city.
Walbank Commentary