Heliopolis was one of the most ancient cities of Egypt and is toady a suburb of Cairo. Originally it stood five miles east of the Nile at the apex of the Delta, but the modern city is some distance away. In ancient times it was the principal seat of sun-worship, thus tis name which means "Sun-town" in Greek.
There appear to have been two forms of the sun-god at Heliopolis in the New Kingdom - namely, Ra-Harakht, or Re-Harmakhis, falcon-headed, and Etom, human-headed; the former was the sun in his mid-day strength, the latter the evening sun. A sacred bull was worshipped here under the name Mnevis, and was especially connected with Etfim. The sun-god Re was especially the royal god, the ancestor of all the Pharaohs, who therefore held the temple of Heliopolis in great honour.
Each dynasty might give the first place to the god of its residence - Ptah of Memphis, Ammon of Thebes, Neith of Sais, Bubastis of Bubastis, but all alike honoured Re. His temple became in a special degree a depository for royal records, and Herodotus states that the priests of Heliopolis were the best informed in matters of history of all the Egyptians. The schools of philosophy and astronomy are said to have been frequented by Plato and other Greek philosophers; Strabo, however, found them deserted, and the town itself almost uninhabited, although priests were still there, and cicerones for the curious traveller. The Ptolemies probably took little interest in their "father" Re, and Alexandria had eclipsed the learning of Heliopolis; thus with the withdrawal of royal favour Heliopolis quickly dwindled, and the students of native lore deserted it for other temples supported by a wealthy population of pious citizens.
In Roman times obelisks were taken from its temples to adorn the northern cities of the Delta, and even across the Mediterranean to Rome. Finally the growth of Fostat and Cairo, only 6 miles to the southwest, caused the ruins to be ransacked for building materials. The site was known to the Arabs as A yin es/i shems, the fountain of the sun, more recently as Tel Hisn. It has now been brought for the most part under cultivation, but the ancient city walls of crude brick are to be seen in the fields on all sides, and the position of the great temple is marked by an obelisk still standing (the earliest known, being one of a pair set up by Senwosri I, the second king of the Twelfth Dynasty) and a few granite blocks bearing the name of Rameses II.
In the Bible Heliopolis is known as On.
The modern city of Heliopolis was created by the Heliopolis Oasis Company headed by the Belgian Baron Empain beginning in 1905. The company bought a large strech of desert some distance to the northwest of Cairo at a low price from the colonial government. It then built a commuter train line connecting it to Cairo and provided the area with roads, water, and vegetation. The city was originally filled mostly with foreigners and native Egyptian Christians, over time, however, it became home to much of Cairo's educated middle class. As Cairo has grown the once large distance between Heliopolis and Cairo has vanished and it is now well inside the city. Because of the large growth in population the original gardens that filled the city have mostly been built over.
Ancient Heliopolis
Modern Times
Some of this entry was originally from the 1911 Encyclopedia Britannica. Please update as needed.