Jeremy Atiyah (30/12/62 to 12/04/06), died suddenly last month while walking in Umbria. Here we publish the last piece he wrote for these pages, a humorous tale from his travels in Egypt

From the back seat of a Mercedes, in the mother of cities, I am looking for an obelisk. "Slow down!" I shout, as we swerve between a group of schoolgirls and a line of parked vehicles. My driver calmly reminds me that we are on an urgent mission: to find relics of the city of On, the most ancient of all the cities ever built here at the base of the Nile's delta.

"But look out!" I cry, as we accelerate to overtake a donkey cart. We are heading into the path of two converging buses. Yet again, we emerge with an inch to spare on either side.

"Number One driver in Egypt," chuckles the driver, as I grip my seatbelt and concentrate on the scholarly words of the Roman geographer Strabo. "It was said," he wrote in the first century BC, "that, anciently, this was the principal residence of the priests, who studied philosophy and astronomy..." In Strabo's day, it was already 4,000 years old, and all he found was a mound and a few stones.

Might any of these stones survive? My driver has assured me that they do: there is an obelisk on a traffic roundabout, in the district of Matariyah, the last surviving relic of ancient On. Only modern Cairo's traffic comes between us and it.

On my first trip to Cairo in 1982, as a 19-year-old back-packer I had no map, guide or money. I saw little beyond my mosquito-infested hotel, which is why I have been so determined to make amends this time round, by covering 6,000 years of Cairo's historic sites in six days (hence driver No 1).

Amid honking traffic, I recall the sites I have seen so far, starting, six days ago, at the southern end of Roda Island, at the so-called Nilometer, the device originally used for measuring the annual flood of the Nile in the whole of Egypt. On a certain day each August, the height of the water was measured here: too little foretold drought, too much foretold floods. Harvests could be predicted and tax levels set throughout Egypt, according to the readings obtained. The Nilometer's tunnels have long been sealed, and the well shaft is dry. But no cities here could have existed without it.

Also on the first day, I made a fast drive up to the heights: to the top of the barren Muqattam, the cliffs of bare stone that impede Cairo's growth to the south-east. Romantic couples come here to canoodle in their cars, gazing down on their vast, smoggy city. From these cliffs, the white sandstone was quarried that clad the pyramids 4,500 years ago.

Dedicating the second day to Egypt's pharaonic remains, I started with the city of Memphis: not quite the first city of the area, but certainly the first imperial capital. From here, Upper and Lower Egypt were united under one ruler for the first time, some 5,000 years ago. Back then, it was the world's greatest city, with granaries, lakes and temples. But all I could see was a mangy dog chasing a woman, and a bullock. Two hundred tourists trudged diligently behind me, wondering what to look at.

Today Memphis is a smallish enclosed park, littered with broken statuary, amid groves of dusty, spiky palm trees. The foundations of the old city lie lost far beneath the ground. I spent a day touring pyramids that date back 45 centuries, starting with the stunning step-pyramid - Sakkara, the oldest freestanding, man-made structure in the world, followed by the "bent" pyramid of Dahshur, so called for the abrupt change in angle of its outside walls.

This was the true Egypt, down to the handsome, rogues sidling alongside me on the backs of camels. Did madam wish to sit on a camel? Did I wish to have my photo taken next to madam? Did I have any baksheesh? I gave them what they wanted."Egyptian Cadillac!" cried a man approaching on a donkey.

I still had the pyramids of Giza ahead of me. After 4,500 years, these have not yet lost their power to astound and awe, even though they now stand on the outskirts of the modern city. The son et lumière shows, the productions of Aida, the encroaching hotels, adjacent golf courses, tour buses, "special price" guides, camels, postcards, picture books, clap-trap - none of these detract from the experience of looking for the first time into the impassive face of the Sphinx, with the Great Pyramid of Cheops filling half the sky.

On the third day, I was ready to turn my attention to the living city of Cairo. Beyond the skyscraping hotels with their splendid Nile views, much of the city seems to have been trampled into the dirt by the supporting pillars of flyovers. Everything has been reduced to a uniform dun colour, thanks to dust blowing ceaselessly off the desert. Much of it, in result, is rendered invisible in the haze, hidden below the level of the roads, disdained, semi-ruinous and forgotten. But it is there. When the Romans came to Egypt, they built a city called Babylon (not to be confused with Babylon in Mesopotamia). What remains of their efforts are not only fortifications, but also culture. The city quarter now known as "Old Cairo", built on the site of ancient Babylon, is still the Coptic quarter of Cairo - the Copts being a relic of the Roman population, pre-dating the arrival of the Muslims in AD641.

Old Cairo today is not a lovely place. Coach-loads of slightly disappointed tourists creep along dusty alleys of cement and bare brick. Wobbling clay-built Roman walls protrude here and there, some conserved, others festering amid piles of rubbish. One of the old towers of Roman Babylon stands outside the metro station, but its base starts 10 metres below the ground. The Coptic churches too are at varying subterranean levels, according toage. The oldest are accessible down excavated steps and are little gems, lined with icons and filched Roman columns.

Cairo's Christian spring was a short one and a long Islamic summer soon dawned. North of Old Cairo is the site of the first Islamic city of the region, Fustat. I arrived here on my fourth day to visit the great Mosque of Amr Ibn al-As - the first in Cairo, dating from the 7th century, a huge white plain of marble, where the world came to pray amid forests of Corinthian columns.

The city of Al-Qahira, founded in 969, eventually became the seat of the Caliphate, and the largest, richest city in the world. This was the fabled medieval Cairo of bazaars, minarets and domes. Much has been lost; much continues to decay and crumble. But splendid mosques and madrassas and palaces survive by the dozen, and a connoisseur could spend weeks here.

I walked round the gorgeously archaic Mosque of Ibn Tulun. I gazed upon the magnificent façade of the madrassa of Sultan Qalaoun. I heard the call to prayer from the tiered minarets of the mosque of Sultan Hassan. I smelled the donkey droppings by the Bab Zuwayla. I browsed the trinkets in the Khan Al-Khalili bazaar. I even picked through the litter-strewn alleys of the Cities of the Dead, medieval cemeteries inhabited by the city's poor.

And I glimpsed the hidden domestic world of medieval Cairo, with its secret salons and invisible courtyards, at the Beit Al-Sihaymi in the Darb Al-Asfar, and in the so-called Gayer Anderson Museum, attached to the Ibn Tulun Mosque, where an eccentric Englishman lived out his orientalist fantasies with a Nubian boy-servant in the early 20th century.

I saved until last the Al-Azhar Mosque, the foremost centre of Islamic learning in the world where, in an atmosphere of utter tranquillity, earnest young men lounged on carpets, reading their Koran and debating in hushed voices.

On the fifth day I charged up to Saladin's citadel, the massive fortifications of which have commanded astonishing views over Cairo since the 12th century. The main structures that survive here today are not those of Saladin, but of Egypt's great 19th-century nationalist, Mohammed Ali. His mosque is purely Ottoman in style, decadent and sumptuous: half-mosque, half ballroom. In the courtyard wall stands a clock given to Ali by the French government in exchange for the obelisk that now decorates the Place de la Concorde. "The French gave us that broken clock!" my guide said in despair. "We are still trying to fix it!"

And so I hastened, on the sixth day, into Cairo's European century. The Paris of Napoleon III was the paradise that Ismail Pasha tried to reproduce here on the banks of the Nile, with its palaces, legations, handsome Italianate villas, leafy avenues, hotels, theatres and cafes. Dribs and drabs of this survive in suburbs such as Garden City, home to the huge British Embassy. But 20th-century Cairo expropriated most of what had gone before. By its end, the city's population had bloated to 16 million, and the amount of parkland per inhabitant could be measured in square inches.

But modern Cairo is not without its pleasures. A million Arab tourists come here each year, to visit its casinos and its opera house, ogle its belly-dancers, read its newspapers, follow its fashions, and to eat and drink in its restaurants and bars. I've tried to join them, drinking tea at Groppi's, dining at pavement cafés behind Ezbekiya Gardens where grilled chicken and rice cost £1, and in swanky Zamalek at Abou Seed, with its seductive music and sophisticated clientele.

"What are you doing?" I gasp, as my driver suddenly hits a speed bump at 50mph. "The obelisk is near!" he cries, accelerating again. We are here, at the fabled roundabout, the location of the last relic of On. What we find is not an obelisk, but a notice, and a laminated picture - of an obelisk.

"By God!" he shouts again, hurtling round the roundabout and putting three traffic cops and a donkey to flight. "The original has been removed!" And Ibeg him to let me walk home.

Abercrombie & Kent (0845-0700 612; abercrombiekent offers four nights at the Four Season Cairo at Nile Plaza from £849 per person, including return flights, transfers and b&b