On the northeast outskirts of Cairo, amid well cultivated fields near El-Matariya, below the Hill of El-Hisn, are the remains of the ancient Egyptian town of Yunu, known in the Greek period as Heliopolis (not to be confused with the Cairo district of New Heliopolis), which is referred to in the Old Testament under its Coptic name of On: thus in the Book of Genesis (41: 45) the father of Joseph's wife, Potipherah (Egyptian Pede-pre, "he whom Re has given"), is described as a Priest of On. Heliopolis-On, one of the oldest cities in Egypt, was capital of the third nome of Lower Egypt and from the Old Kingdom onwards the spiritual and ecclesiastical center of the whole country.HistoryThe local deities were the falcon headed Re-Harakhty, the sun god, in whose honor the Greeks named the city Heliopolis ("City of the Sun"), and the human headed Atum, with the sacred Mnevis bull. To these deities was dedicated the famous temple, the "House of Re", built by the first King of the 12th Dynasty, Amenemhet I, on the site of an earlier temple. Two large obelisks were set up in front of the temple by his son and successor Sesostris (Senwosret) I in celebration of his jubilee. Much of the religious literature of Egypt originated with the priests of Heliopolis, and their doctrines were widely disseminated throughout the country at a very early period, making Re-Harakhty one of the most highly venerated Egyptian deities. During the Greek period they still enjoyed a great reputation for wisdom: Herodotus conversed with them, and Plato is said to have spent 13 years with them.Under the New Kingdom the Temple of Heliopolis was the largest and wealthiest in Egypt after the Temple of Amun at Thebes. When Strabo visited Egypt (24-20 B.C.) the city was destroyed and deserted, but the temple still stood intact apart from some minor damage attributed to Cambyses; even the priests' houses and the lodgings occupied by Plato and his friend Eudoxus were still shown to the traveler. The priestly school, however, had been closed, and only a few officiating priests and guides for visitors still lived there.There are only scanty remains of the ancient city (estimated to have been some 1,200yd/1,100m long and 550yd/500m across) or of the Temple of Re-Harakhty, the buildings having been demolished to provide stone for the building of Cairo. The archeological exploration of the site is made difficult, and sometimes impossible, by the extent to which the area has been built up. Scattered about in the fields are a few remnants of the double wall of brick which once surrounded the city.
All that remains of the temple is a solitary obelisk (Arabic El-Misalla) of red Aswan granite, 67ft/ 20.42m high. Each of the four sides bears the same inscription in large hieroglyphic characters, recording that Senroswet (Sesostris) I, "King of Upper and Lower Egypt, lord of the diadems and son of the Sun, whom the (divine) spirits of On love" set up the obelisk on his first Sed festival (a kind of royal jubilee). The pyramidion at the tip of the obelisk was originally gilded, as were the falcons at the beginning of the inscriptions. The counterpart of this obelisk (for the obelisks in front of temples always stood in pairs) fell in the 12th C. In addition to these two Heliopolis had many other obelisks, one of which now stands in the Piazza del Popolo in Rome. It is known, in the light of modern research, that Heliopolis possessed at least ten temples, all probably associated with the principal temple or perhaps even forming part of it.
In the desert some 3mi/5km east of the obelisk is the Necropolis of Heliopolis, dating from the Middle and New Kingdoms. A notable feature of the Middle Kingdom tombs was the large numbers of weapons found as grave goods.
1mi/1.5km northeast of Heliopolis, at Tell el-Tawil, were bull burials.
In front of the Chapel of the Virgin in the nearby village of El-Matariya, a popular place of pilgrimage in the Middle Ages, is the so-called Virgin's Tree, a sycamore planted in 1672 in replacement of an older tree. According to legend the Virgin and Child rested under the shade of a tree here during their flight into Egypt. The little garden in which the tree stands is watered from a spring, said to have been called into being by the infant Jesus, which yields good fresh water, whereas the water of all the other springs in the area is slightly brackish. The legend of the Virgin's tree links up with an older cult; for the ancient Egyptians venerated a tree in Heliopolis beneath which Isis was believed to have suckled the infant Horus.
In the southeast corner of the temple precinct tombs of High Priests of the Sixth Dynasty were found, in El-Matariya tombs of the Late Period.