Alexandria was a city in Egypt, home to the largest library in the ancient world. (PROSE: The Book of Shadows) The Doctor had a bit of a chequered history with that library. On one occasion, the Fourth Doctor was forcibly ejected from after shelving the Dead Sea Scrolls improperly. (PROSE: Eye of Heaven) On another, the Seventh Doctor saved two Aristophanes plays from the burning of the library. (PROSE: Timewyrm: Apocalypse)
During the reign of Ptolemy I, Astrolabus helped build a lighthouse in the city, taking fire from the Sun and stars to do so. Spacecraft came from space to the city, and it became a crossroads in time and space for such visitors. They sought Voyager's star charts, but adepts in sorcery called upon chthonic winds and fled with the charts. With the city's fall and the conjunction of Mars, Jupiter and Saturn, creatures from the depths of the sea, including the Kraken, rose and destroyed what remained of Alexandria. (COMIC: Voyager) At another point in Ptolemy's reign, the First Doctor, Ian Chesterton and Barbara Wright visited the city. (PROSE: The Book of Shadows)
In the 4th century AD, the city was a hotbed of politico-religious intrigue. Two schools of thought — one represented by Alexander of Alexandria and the other by Arius — struggled for predominance in the Christian church. The row became so fractious that the Roman Emperor Constantine had to step in and call a Council at Nicaea to settle things and restore order to the church and the empire. At issue was the question of whether Jesus Christ was literally created by God, or whether, as part of a Holy Trinity, the two were aspects of the same entity. Alexandria and its place in the debate were so well known that even common folk in Nicaea knew of it. (AUDIO: The Council of Nicaea)