The Egyptian name Iunu is commonly rendered as the Pillar City. Its ancient site lies around Al-Matariya and Ain Shams, rather than being identical with the modern Cairo suburb that later received the Greek name Heliopolis. For generations, rulers supported the solar sanctuary with buildings and offerings. Worship linked the movement of the sun with the maintenance of an ordered world. The title Son of Ra connected Egyptian kingship with that solar power, but no single city invented every form of royal religion. Heliopolis was one influential centre within a country whose temples preserved overlapping and sometimes different accounts of the gods.

One of its best-known creation traditions begins with the primeval waters of Nun. Atum emerges as the self-generated creator, and from him come Shu and Tefnut. Their children are Geb, the earth, and Nut, the sky; the next generation contains Osiris, Isis, Set and Nephthys. Together with Atum, these figures make the nine of the Ennead. The divine family connects the formation of the cosmos with the later stories of conflict, death and restored kingship. These accounts were religious explanations, not reports of observable events. Heliopolitan theology was important, but it did not erase the creation traditions associated with Memphis, Hermopolis or other sacred centres.

The Benben Stone expressed the first emergence of land and the appearance of creative power. Its associations helped connect the sanctuary with the pointed forms and solar symbolism of Egyptian monuments. That does not make a surviving benben the demonstrable blueprint for every pyramid or obelisk. The Bennu bird belonged to the same religious landscape of creation and renewal. Later comparisons connected this Egyptian bird with the Greek phoenix, although their traditions should not be treated as identical in every detail. The Mnevis bull was another sacred presence at Heliopolis, a living animal honoured within the solar cult. Stone, bird and bull expressed different forms of a divine world rather than a single fixed image of the sun.

Kings made that devotion monumental. Senusret I of the Twelfth Dynasty erected obelisks at Heliopolis, and one survives at the ancient site. Rising about twenty metres, it is a major standing witness to a temple landscape that has largely disappeared. Later rulers added their own monuments. The sun temples of the Fifth Dynasty also belong to the wider growth of royal solar worship, but those kings continued building pyramids: devotion to the sun did not simply replace royal pyramid burial. The relationship between solar cult and kingship developed through several kinds of sacred building.

Some of Heliopolis's obelisks travelled much farther than their royal patrons could have anticipated. Two commissioned by Thutmose III were moved to Alexandria in Roman times and much later to London and New York. They became known as Cleopatra's Needles, despite having been made more than a thousand years before Cleopatra VII lived. The New York monument was installed in Central Park in 1881. Their journeys changed their setting and the meanings attached to them. Once statements of Egyptian royal worship, they became diplomatic gifts, engineering challenges and city landmarks. Their carved names still connect them with the sanctuary from which they were taken.

Other traditions preserved the city in words. Genesis identifies Joseph's wife Asenath as the daughter of a priest of On; that is part of the biblical narrative, not independent archaeological confirmation of every event in it. Greek writers admired the reputation of Heliopolis's priestly learning. Strabo, however, described a diminished place, with the old scholarly pursuits no longer flourishing as before. His account cannot be used as evidence for an unchanged, thriving university town. Later dismantling, reuse and urban growth further transformed the site. The surviving obelisk and excavated remains preserve parts of its material history, while its creation traditions retain a much wider life in the study of Egyptian religion.