IRAN/Letter from Tehran: Wafting out of chai houses from the slums of south Tehran to the glamorous restaurants nestled in the hills of north Tehran, the heady, rich aroma of the hubble bubble hangs like a cloud in the hot summer air.
This is café culture Iranian style - soon to banned by hardline conservatives.
Obligatory with a glass of black, bitter tea and a requisite way of ending a meal, smoking the hubble bubble, or the qalyoun as it is known in Iran, is serious business, entrenched in Iranian culture for centuries.
Travel guide Lonely Planet advises its readers that smoking the pipe is "the greatest act of cultural integration that a foreigner can make in Iran, short of converting to Shi'ite Islam".
Young Iranians flock to the mountain retreat of Darrakeh to indulge in a relaxing puff. Here they enjoy a greater degree of freedom, away from the eyes of the police who are deterred by the steep mountain tracks. Descending deep into a valley, with kebab houses lining a gushing mountain river, couples openly hold hands, burst into song and smoke the qalyoun. Women were banned from smoking the qalyoun in public three years ago as it was deemed morally inappropriate.
But in Darrakeh, mixed groups are led to discreet areas tucked away behind trees. They lounge on wooden beds covered with Persian rugs passing the pipe to each other - the more adventurous sprinkle hashish on the glowing coals for a stronger buzz.
They laugh, flirt and discuss the latest news while gulping in lungfuls of sweet, soothing apple tobacco, just like a group of friends meeting up for a pint at the local boozer. And this, it seems, is where the problem lies.
"By banning the qalyoun, they're trying to control the gathering of people, because when people sit around that pipe, they start talking about politics," said Cyrus Donyai, a seasoned qalyoun smoker and a regular at the Shariati tea house in downtown Tehran, where smoking sessions frequently erupt into passionate political debates.
Ostensibly, the war the conservatives are waging against the hookah is for health reasons - they say the pipe is unhygienic and can pass diseases.
But strict religious scholars have always maintained that the head rush induced by a few drags is racy stuff, and therefore un-Islamic. Some also think that the sight of a women sucking on a such a long instrument is too suggestive to bear. And there's the niggling fact that most of the glass bowls of the qalyoun, in which the water gently bubbles as the tobacco passes through, are imprinted with the majestic image of the moustached Nassredin Shah, a famous Qajar King.
The ban is also part of a summer crackdown, due to the sweltering heat precipitating loosening moral values - shorter manteaus, diaphanous headscarves, ankle-flashing trousers - and to the change-over of power in February from the reformists to the morality-obsessed hardline conservatives.
There have been several raids on popular fast food restaurants where teenagers hang out, and undercover morality police have been patrolling Jordan and Ferestheh streets - the main pick-up joints where young Iranians cruise - hauling unrelated boy and girls out of cars.
Darrakeh is unusually quiet for a Wednesday night. All of the wooden beds are empty, except for one where a group of students study for their exams.
Restaurants have been warned that they will be heavily fined if they are caught in beach of the new law.
"We will be rigorous in dealing with the promoters of vice and fornication," reformist daily Sharq quoted Tehran prosecutor Saeed Mortazavi as saying.
"This is ridiculous," protests a customer on reading the notice at the entrance of a tea house. Laleh had been looking forward to unwinding with an evening qalyoun after a hard day studying law at university.
The owner of the tea house rubs his forehead as he nods in silence. On the same day last week he made $150, even though university exams was keeping Tehran's students indoors. Today he has made just $40. "This is going to be the ruin of me," he says. "They're playing with our lives."