Caesar entered Alexandria in triumph, but was then attacked by the citizens and Ptolemy XIV's army and had considerable difficulty in maintaining his position in the Regia or "Royal City". Cleopatra was able to win over by her charms first Caesar and later Antony, who lived with her in Alexandria from 42 to 30 B.C. Augustus enlarged the city by
the addition of th suburb of Nicopolis. At this prosperous period Alexandria was said to have a population of more than half a million; the Greek element predominated, followed by the Egyptian, while there was also a separate Jewish community, originally established in the time of Ptolemy I.
In A.D. 69 Vespasian was proclaimed Emperor by the citizens of Alexandria, largely as a result of the influence of the philosophers of the Museum. In the reign of Trajan (98-117) the Jews, who then constituted a third of the population, were the cause of bloody riots. In the year 130 the Emperor Hadrian (117-138) visited Alexandria and instituted public disputations in the Museum. Marcus Aurelius (161-180) attended the lectures of the grammarians Athenaeus, Harpocration, Hephaestion, Julius Pollux and other scholars. During this period, too, the Greek satirical writer Lucian lived in Alexandria as Secretary to the Prefect of Egypt. Septimius Severus (193-211 ) visited the city in 199 and granted it a municipal consitution. The next Imperial visit was disastrous, for Caracalia (211-217) was derided by the citizens and revenged himself by a bloody massacre and the closure of the Academy. Alexandria suffered still more cruelly during the fighting between Palmyrene and Imperial forces in the second half of the third century, when a large part of the population was carried away by the sword, famine and pestilence.
Christianity established itself in Alexandria at an early stage. According to tradition the Gospel was first preached here by St Mark (whose remains were carried off to Venice in 828). The first great persecution of the Christians in the reign of Decius (250) hit Alexandria hard. The city had been for many years the seat of a bishop, and had had since 190 a theological school, presided over by Pantaenus and, at the beginning of the third century, by Clement of Alexandria, which sought to combine Christianity with the Neo-Platonism which developed about this period and was taught by Ammonius Saccas, Herennius, Plotinus, Porphyrius, lamblichus and others. A second persecution took place in 257 during the reign of Valerian, and soon afterwards, in the reign of Gailienus, plague carried off a large part of the population. Nevertheless Alexandria still remained the principal seat of Christian learning and the orthodox faith (Athanasian Creed) until it was compelled to yield this position to the newly founded city of Constantinople. Sanguinary quarrels took place between the Athanasian party and the Arians under their unworthy bishop Georgius. During the reign of Julian the Apostate (361-363) the Christians of Alexandria were again persecuted. Under Theodosius (379-395), however, paganism received its deathblow. Patriarch Theophilus of Alexandria showed the utmost zeal in destroying pagan temples and monuments, and the famous statue of Serapis was destroyed by fire. The material prosperity of the city now declined, so that it could no longer meet the cost of cleansing the Nile and keeping the canals open. Its revenues were reduced still further when the Jews were expelled from the city by Patriarch Cyril. In 415 the learned and beautiful pagan Hypatia, the principal opponent of the fanatical Cyril, was stoned to death by a mob. The pagan schools were finally closed during the reign of Justinian (527-565).
In 619 Alexandria was captured by King Chosroes II of Persia, but the Christians were not molested. In 626 the Persians were driven out by Heraclius; but soon afterwards the armies of the Caliph Omar advanced into Egypt under the banner of Islam, and in October 641 the city was taken after a prolonged siege. Omar's general, Amr ibn el-As, treated the inhabitants with moderation; but Alexandria now continued to decline, while the new capital of Cairo prospered. The discovery of America and the sea route to India finally destroyed the city's commerce.
The decay of Alexandria, which by 1800 had a population of only 5,000, was finally arrested by Mohammed (Mehemet) Ali, who improved the harbor and constructed a number of canals. His main contribution was the construction of the Mahmudiya Canal (begun in 1819), named after the reigning Sultan Mahmud II, which irrigated the surrounding country and linked Alexandria with the rest of Egypt, whose products had hitherto been shipped from Rosetta and Damietta. Subsequent rulers also sought to improve the position of the town. During Arabi's Rising in 1882 much of the European quarter was burned down. Thereafter, however, Alexandria began to recover its prosperity, and it is now the largest and most important city in Egypt after Cairo.
The Royal Library of Alexandria, founded at the beginning of the 3rd century BC, was once the largest library in the world. It was destroyed by fire on a few occasions. The Bibliotheca Alexandrina is a major library and cultural center, completed in 2002, to commemorate the Royal Library and keep the sense of Alexandria as a center of study.
Alexandria has many notable landmarks such as the Roman Amphitheatre, Pompey's Pillar, Montaza, and Maamoura Beach, one of the main tourist attractions of Alexandria. The city is a popular summer resort for tourists in the Middle East who come to enjoy the sun and sea.