But then you can't do much about aerial sewage - what you can protect yourself against is crime and fear. The hijacker who wants your car will shoot a black businessman as easily as a white housewife. Jo'burg is the city of beautiful walls where people fortify their houses, barricade their flats, electrify their fences, buy dogs and guns. Or they move into cluster-villages, gated, guarded and patrolled round the clock. They all sell freedom from fear - but Dainfern does it better, and does it with style.

What segregates South Africans these days is security, and how much of it you can buy is what separates the saved from the servants. Dainfern is the answer to the Jo'burgers prayer - to live an unlocked life in a safe place where no bullets fly and hijackers fear to tread.

The day I went to Dainfern, sunshine lay like honey on Highgate Village, children played in Waltham Drive and the golfers trundled in electric carts over the fairway. Hugo is Swiss and has lived here for years. He likes to tell visitors that the pipe in the sky is the track of the new high-speed train that will one day dissect Gauteng. Hugo calls this extravagantly expensive golfing stockade "just a ghetto for whitey", but then Hugo has a mordant streak of humour. All sorts are welcome in Dainfern, if you can fork out the readies - it's cash, not colour, that counts.

Dainfern's achievement has been to persuade those behind its walls that this isn't a penitentiary, it is a paradise; it's not a life-sentence, it's a "lifestyle". "No one who is not supposed to be in here is in here," the managers of Dainfern told me in tones that might well apply to those confined in less happy institutions. But I got their drift. Anyone not meant to be in Dainfern runs the risk of being electrocuted, shot or arrested.

Embedded in the walls that ring Dainfern are seismic sensors; and reinforced steel bars reach down 10ft in to the earth to stop human moles who might tunnel beneath the fortifications. Detectors along the length of the perimeter wall listen for incursions. An electric fence tops the wall and carries enough current, a polite notice warns, "to cause death". Closed-circuit cameras constantly check the perimeter defences and in the gatehouse control-room, staff screen and record every visitor who comes and goes. Rapid reaction vehicles stand ready, and frequent armed patrols glide down Collingham Close and Willowgrove Road.

Patricia has lived here for years and got to the heart of what makes Dainferners happy. "What we have here is the way it was. When you could stroll through your neighbourhood, and leave your windows open. When your kids took their bikes and rode down to the river.What we're doing is remaking the life of the 60s in the new millennium."

John, a British builder, didn't buy into Dainfern for the golf - "Can't stand the game ." He was after the good life. Helicoptering over the area, he saw peaceful green acres and beautiful walls and said, "Right, I'll have one of those." "Those" are the Dainfern mansions, ranging in style and taste from the opulent to the preposterous, from "Tuscan" to "French provincial" to a popular hybrid called "African Zen".

Brenda, an estate agent, bought here long before many others. Dainfern houses reflect a pecking order: the smaller places and they are very small go to those who can shell out a couple of million "for the address". The mansions belong to those who lavish a fortune on pilasters, crystal, koi and in-house movie theatres, and a litter of Porsches crowd the front yard. But it is not just about money, she said, and I heard it over and over - "it's about living".

Dainfern's bucolic illusion is achieved by brilliant recreational engineering. It is nature trails, plashing fountains, green vistas and strolling guinea fowl. This is Jo'burg's unlikely Eden - it prefers the well-heeled to the well-shriven, the rich over the righteous, and instead of angels posted outide its gates with flaming swords to keep out the riffraff, it has guards with guns and thousands of volts pulsing through the fence. It is not an anachronism in the new South Africa, however; it is the future.

Dainfern is selling what other, far more opulent islands of rich isolation such as "Carefree" in Arizona, or the gargantuan Beverley Springs in California , are selling - safety in a dangerous world. These "lifestyles" are posited on the idea that you can, if you are rich enough, buy yourself out of the nation-state and into high-security nirvana built to your specifications. In the old South Africa, only black people lived in "townships"; in the future South Africa, the planners of Dainfern have realised, everyone will live in townships.

There is indeed very little difference between the millionaires' enclosure of Dainfern and the whites-only Afrikaner township of Orania that I visited not long ago. In fact, Orania is probably more independent since it does not rely on outside staffing. These futuristic high-security sybarite compounds - and they are springing up everywhere north of Johannesburg - boxy, walled-in hutches with none of Dainfern's space and strange serenity - must be serviced, usually by low-end suppliers in nearby satellite villages. And Dainfern has not one but two of those, and the silver pipe in the sky connects them like an umbilical cord.

Diepsloot ("deep ditch" ) is just down the road. It is a vast, apocalyptic place of rutted roads, shacks, houses, thin children, thinner goats, constant cooking fires, constant funerals, dirt roads, and dust. To stand on its outer edge is to see it literally spreading towards the reinforced walls of Dainfern. You do not see white faces in Diepsloot.

Lucas, 20, lives in Diepsloot and works as a security guard over in Dainfern. He says: "Maybe they don't like our smoke, maybe they don't like our taxis, but they like our muscles."

In early July a rumour went around Diepsloot that residents were to be moved to new housing miles away and the township errupted in riots that went on for days. Of those riots Thembi, who is out of work and 18, says: "It wasn't true that we were moving, but people thought it was true and they got very angry. This is home."

The July riots shut down the entire area and they were the worst seen since South Africa put the apartheid era behind it. Cars were stoned, reporters attacked, police fired rubber bullets and many were arrested. I heard from Moses, a gardener over in Dainfern, a phrase used again and again about those riots: "God's anger broke loose." Young Mathoba told me he stoned the journalists because "you have to talk to someone". The bitterness in Diepsloot was not directed at Dainferners but at the city council that "is more corrupt than the old apartheid people," said Sophie, a maid in Dainfern - "Big jobs and good times for bigwigs - no house, no hope for us."

South Africa right now is not much interested in history; all the talk is of the "new". But history goes on being terrifyingly interested in South Africa. Close the door on the the past and the ghosts come through the window. So it was that one morning, on a patch of veld hard by the fine walls of Dainfern, I met a man called Lucky directing a team of diggers from Tsogo Funerals, searching for forgotten graves of people who once lived on the old farms that became the giant new walled estates. Clans like the Bapong, the Sithole and Monanereng lived here for centuries. Tradition requires that ancestors be honoured, shown a new-born child, or consulted about a marriage or respected with flowers or soothed with a pinch of tobacco snuff.

"How can this happen," asked Lucky, "if you don't know where they are buried?"

The developers of the great walled suburbs are sure all ancestors were exhumed and reburied. Lucky and the relatives of the lost ancestors dispute this. Lucky suspects that some of the missing ancestors may lie buried beneath the Italian tiles and parquet floors of Dainfern. There is a court case in progress, and tempers are frayed.

Lucky says: "I'm not bitter, I am very patient. The new owners have have legal title to the land they have bought and developed. But if I wanted to make my point I'd say that before them - before your ancestors ever arrived in Africa - our people were here, lived here, died here."

Sunlight mixes with red earth as the gravediggers sift the soil. One of the gravediggers is waist-deep in the trench when his mobile phone rings - a snatch of rap jingles in the veld; the man stops, does a little shimmy while the music lasts, and then goes back to his digging.

In the meantime, life goes on: the residents of Dainfern stay put while residents of Diepsloot lucky enough to have jobs move between township shacks and Tuscan mansions in their guise as florists and builders and security guards. In this phantasmagoric city, maybe that's one way of spotting who the real South Africans are - they have to lead more lives.

It is not always remembered that, in South Africa, it is blacks and not whites who are most at risk from shootings, rapes and robberies. Given the choice, I have no doubt Diepsloot would opt for the hermetic happiness of Dainfern. Anyone who imagines that Dainfern represents some kind of short-lived aberration has not been looking hard at South Africa.