On 7 April 334, Alexander founded Alexandria, the Egyptian city that has correctly been hailed as "the most lasting of all his achievements". The Greek author Plutarch of Chaeronea, describes the event in section 26.3-10 of his Life of Alexander.
The translation was made by M.M. Austin.
The foundation of Alexandria
[26.3] If what the Alexandrians say on the authority of Heracleides is true, then it seems that Homer was no idle or useless companion to him on his expedition.
[26.4] They say that after his conquest of Egypt, Alexander resolved to found and leave behind him a large and populous Greek city which would bear his name. On the advice of his architects he was about to measure out and enclose a certain site,
[26.5] when during the night, as he was sleeping, he saw a remarkable vision. He thought he could see a man with very white hair and of venerable appearance standing beside him and speaking these lines:
Then there is an island in the stormy sea,
In front of Egypt; they call it Pharos.note[Homer, Odyssey, 4.354-355.]
[26.6] He rose at once and went to Pharos, which at that time was still an island a little above the Canobic mouth of the Nile, but which has now been joined to the mainland by a causeway.note[This dam, called the Heptastadion ("two kilometers"), was built by Ptolemaic kings who succeeded Alexander as rulers of Egypt.]
[26.7] When he saw that the site was eminently suitable (it is a strip of land similar to a fairly broad isthmus, running between a large lagoon and the sea which terminates in a great harbor), he exclaimed that Homer was admirable in other respects and was also an excellent architect, and ordered the plan of the city to be drawn in conformity with the terrain.
[26.8] Since there was no chalk available, they used barley-meal to describe a rounded area on the dark soil, to whose inner arc straight lines succeeded, starting from what might be called the skirts of the area and narrowing the breadth uniformly, so as to produce the figure of a mantle.
[26.9] The king was delighted with the plan, when suddenly a vast multitude of birds of every kind and size flew from the river and the lagoon on to the site like clouds; nothing was left of the barley-meal and even Alexander was much troubled by the omen.
[26.10] But his seers advised him there was nothing to fear (in their view the city he was founding would abound in resources and would sustain men from every nation); he therefore instructed his overseers to press on with the work.