Young people from the San Francisco Bay Area drive to the Nevada salt flats and spend days in the desert building a city for 20,000 attendees

We're coming up to Labour Day weekend: a relic of a now barely recalled battle between US workers and bosses in the late 19th century.

It was presented as a sop by President Cleveland in 1894 to calm the populace after a vicious stretch of strikes. Cleveland wasn't re-elected.

I imagine, in retrospect, the working people took the gift of a one-day holiday as a bit of an insult. The US remains a country curiously disinterested in enforced leisure of any kind. Running dog capitalist bosses or not, a lot of Americans seem to rather like work or, at least, find it hard to stop.

There's no better illustration of this than Burning Man, Silicon Valley's adopted Labour Day festival. A day off in the summer for most of us is an excuse to pull up a deckchair and indulge in some heavy-duty pool paddling.

For the Burning Man festival, the young of the Bay Area drive 300 miles to the middle of the desolate Nevada salt flats, spend days in the desert sun building a city for the 20,000 attendees from scratch, spend a few precious days admiring their work, then burn it all down to the ground. Then the organisers spend the next six months meticulously cleaning the site of any trace of the encampment, before beginning the cycle all over again.

Building a city from scratch is no exaggeration. Black Rock Desert, the home of Burning Man, is 500 square miles of ancient lake bed. Pancake flat and trapped high in the mountains of northern Nevada, it is so dry and alkali that, by August, no plant or animal life can be seen on its surface - just parched and cracked mud as hard as concrete, for as far as the eye can see.

This is one of the driest places on earth; if you don't drink four litres of water a day, you can die of dehydration before you feel thirsty. The daytime temperature can reach 45 degrees centigrade; at night, it drops close to zero.

There's no infrastructure, no electricity or other utilities. There are regular dust storms of speeds up to 80 m.p.h. The closest habitation is Gerlach, Nevada, 15 miles away, but Gerlach's population of 430 is dwarfed by the temporary desert city and Burning Man attendees know well enough not to depend on the locals. They bring all their own supplies.

It's like camping on Mars but somehow the collective willpower and, over the years, the growing expertise of Burning Man's attendees manage to protect and serve its brief population.

The expansion of the temporary city is almost a lesson in civic planning. Money and advertising are forbidden but the system of bartering has, over time, settled into a stable economy. Everyone is expected to co-operate on shared services, pooling and exchanging vitals like shade, water and sunblock.

As the festival has grown, new amenities have evolved. Two years ago, civic-spirited festival goers built a free public transport system (an old bus, dressed up as a giant, fire-breathing dragon). Last year, a postal service spontaneously arose (the postmen took payment in cold water showers and vodka). Policing, fire and crowd control are all largely maintained by the festival's own volunteers.

And, inevitably, for the last three years, Burning Man has had the internet. Strung around the four-mile wide encampment by borrowed aerial repeaters, delivered to individual tents by cheapo 802.11 laptop cards, hitched to the global network by satellite, theoretically this temporary city has 2MB to every home. It's broadband connectivity that most in the Republic - and, frankly, in the majority of Silicon Valley - would kill for.

It's not used much. The technicians who built it and work on this hardware every day of their lives, did it just to see if they could, and to add another amenity to the city.

It's easy to imagine the geeks of Silicon Valley as emaciated brainiacs, disconnected from the real world by their machines. That's not how it is and Burning Man proves it. Many of the geeks here are as at home with a lathe or handsaw as they are with a compiler and debugger.

The same, incidentally, goes for San Francisco's artistic community, who bear most of the burden and triumph of organising Burning Man. These muscled, bespectacled, tattooed and blow-torch-wielding pragmatics are not the effete suburban scoundrels of most modern European art.

The work - this holiday city for the Burning Man festival - that is created between these two communities is reminiscent of the early dotcom boom. Back then San Francisco's position as the avant garde of the Web-design world was forged by an alliance between these artistic communities and the garage-gadget monkeys of the Valley.

The co-operation stumbled when the money men swept in. They enrichened a few of the pioneers and dismantled the communities they came from by making central San Francisco too expensive for anyone but themselves.

Returning from Black Rock City to San Francisco, that's perhaps the starkest contrast. Compared to the chaotic but civic functioning of the Burning Man tent community, San Francisco and Silicon Valley these days are positive shanty towns of mismanaged town planning.

The Valley, scarcely depopulated after the boom, still chokes on the commuters that cram its freeways every morning and afternoon. Its richest inhabitants cloister themselves up in the mountains above the 25-mile-long industrial estate, while below, 29 abandoned factory sites ooze dangerous chemicals, byproducts of the chip-manufacture process, into ground-water, monitored nervously by federal watchstations.

Within the borders of the city, financial mismanagement, political infighting and pandering to the dotcom boom has lead to a collapse in affordable housing and an explosion in the homeless.

As the city's youth improvise their own irrigation and sanitation system in the desert, the politicians quarrel endlessly over whether the homeless should be forbidden to defecate in the streets.

It didn't used to be this way. But just as Burning Man has continued to benefit from the co-operation of geeks and artists, so San Francisco has spurned them, grown fat and complacent, and lost its knack of outliving its own booms.