RENO, Nev. — Thousands of people are flocking to the desert to build a temporary city from scratch for a week before burning and tearing it down.

The annual event known as Burning Man officially begins Sunday, drawing 70,000 people to an otherwise inhospitable desert plain two hours north of here. Participants will build an airport, stage all-night dance parties and bask in a dusty free-for-all with rampant nudity and outrageous costumes. Within days of its Sept. 4 end, the entire city will vanish and the desert returned to its natural state for another year.

Burning Man is not exactly a concert or a music festival, although it has those elements. Instead think fantastical, whimsical art scattered through a tent city, with half-naked people giving away French toast near an orgy dome, while neon-lit buses cruise through and techno thumpthumpthumps all night long. Tickets – which started at about $500 and sold out immediately — come with a long list of conditions of participation, including self-reliance, “radical inclusion” and de-commodification.

“This is having fun for the sake of having fun, making art for the sake of making art, as opposed to having an agenda,” said Tracy Gillan, 38, a 10-year “Burner” and account executive for an online search engine in New York City.

Of course, de-commodification applies only on site, and as they gear up in Reno, participants are spending millions of dollars at big-box stores as they stock up for a week in which there are no commercial transactions — except ice, coffee and RV pump outs — and they just bring in everything they'll need to eat, drink and wear. Advertising and sponsorships are also banned, and organizers encourage participants to cover up or cheekily modify commercial logos.

Staged annually for decades outside the 200-person town of Gerlach, Nev., the ephemeral Black Rock City draws internationally, but with a heavy participation from young California-based software engineers, app developers and tech workers who crave the chance to build physical structures and artwork in an environment where cell phones generally don't work. The event draws its name from the burning of a wooden effigy, which this year will stand 40 feet tall and will burst into flames amidst a massive fireworks display on Sept. 2.

"It is what you want it to be. Music. Art. Dancing. Food. Design. A party. It's what you go looking for,” said Jacob Wilson, 31, who works in content marketing in Manhattan and is attending for his second time. “You’re inhabiting a piece of land no human should be in. It’s pure magic.”

The event itself tries hard to be egalitarian, but some obvious facts stand out: 80 percent of participants are white, 40 percent are from California and nearly 60 percent of the people here live in households earning more than $100,000 annually. All that money means people can afford to give away food and drink, known as “gifting.” Some camps host open bars each day, while others give away waffles or grilled cheese or cold-brewed iced coffee or massages or foot baths.

Participants adopt whimsical names and generally wear elaborate costumes, in part to block the ever-present dust. Other people wear nothing at all, or go around “shirt cocking,” which is when a man wears a shirt but no pants. There’s lots of bare flesh on display, and the community self-enforces against outright ogling or exploitative photography. And reporters and commercial photographers must have to agree to Burning Man’s strict control on copyright.

More:Why you shouldn't eat the gummy bear pyramid at Burning Man

More:Burning Man gets permit, officially not canceled

Nudity and drug use – both of which are present – are illegal on the federally owned site, and volunteer rangers from Burning Man, along with federal and local law enforcement, monitor the event, although they tend to operate with a light hand at an event that pours an estimated $55 million annually into the northern Nevada economy.

For many participants, Burning Man is a chance to set aside the lives they must lead in the real world and enter a fantasyland where lasting friendships will be forged among the swirling dust storms, all-night dance parties and silent sunsets. California-based software engineer Sarah Bravo, 23, who goes by the Burning Man name of “Toilet Patrol,” said she struggles to describe the event to outsiders.

"I change it up every time and it doesn't seem to get across,” she said. "It's just magical."