Heat and dirt, the two plagues of Middle Eastern cities, long ago consumed this fat, overpopulated capital. It has been Mr Karbaschi's post-revolutionary task to accept the first, God-given, burden, and reduce the second in the name of Islam.
"My primary job as mayor is to clean this city that I'm in charge of," he says. "Even in our faith, the sharia talks of taharat, the Islamic word for cleaning." Mr Karbaschi, a small, thin man with frameless spectacles and a neatly clipped beard, 44 years old but prematurely greying, is a close friend of President Ali Akbar Hashemi Rafsanjani and uses his powers accordingly. In the six years since he became mayor, Tehranis have found their parks replanted, their streets swept of garbage and their traffic jams eased.
Private cars are now restricted in the city centre, police bribery has been reduced, 300Volvo commuter buses have replaced the old British Leyland double-deckers and an experimental trolley-bus line. Iranian engineers have recommenced construction of the old French Metro scheme which will - if Mr Karbaschi has his way - cover 30 miles of underground track using Chinese-built trains.
It is a little disconcerting to sit next to a man who uses Islamic philosophy to reconstruct his city, whose department instituted new laws "at the request of the people and some religious authorities" to separate men from women on the new buses - women, of course, have to sit at the back - and whose post-mayoral ambitions are said to run no further than a return to philosophical studies in the holy city of Qom. Is this really enough for a man who controls 9 million - some say 12 million - souls?
To be fair, Mr Karbaschi does not blame his problems entirely upon "the previous regime", upon the Shah Mohammed Reza Pahlavi's massive expansion of private-car ownership which clogged the ancient Qajar capital with Los Angeles-style traffic jams. He has also to contend with the massive immigration of tens of thousands of peasants following Ayatollah Ruhollah Khomeini's revolution. Mr Karbaschi reckons the subsequent, sudden surge of illegal building created a series of unplanned satellite cities - "in total violation of all building codes" - adding one and a half million to the population, a new squatters' metropolis without fresh water or sewers, which is much on the minds of Mr Karbaschi's officials.
The Pahlavis never built a sewage system for their rapidly expanding, imperial capital; for hundreds of years, the city's detritus merely sank into the earth, the rich installing sumps in their gardens, the poor allowing their sewage to run into the increasingly filthy open water drains, jubes, which trickle downhill, fresh through the bourgeois streets of north Tehran and then, ever more polluted, through the southern slums. When the French began construction of the Metro during the Shah's regime, they tunnelled not through rock or clay but compacted and still viscous faeces.
Mr Karbaschi's engineers have constructed a series of boreholes to drain away this awful mud so that the tunnels can be built on solid foundations. His reference to taharat specifically refers to the lavatory. "The mud is not so much a problem now," he says. "Even in London you have been able to build on swamp - look at your office block at Canary Wharf. Yes, I know where the Independent's offices are. There is no specifically Islamic system of town and urban planning but we can at least have an Islamic character to our city. Muslim cities were traditionally clean and had many gardens."
Under the previous [the Shah's] regime, "it was decided that to show your patriotism and nationalism, your family should own a car made in Iran, the Peykan," Mr Karbaschi says. The British-built Peykan plant, manufacturing the old British Hillman, produced millions of vehicles which still pack the streets of Tehran. "The regime filled our city with cars and no one wanted to take the old double-decker buses. A culture had been introduced in which people thought they all had to own a car."
When new laws forbade private cars in the city centre, drivers began bribing the traffic cops. Mr Karbaschi's department issued special permits which motorists could purchase if they wished to enter the city in rush hour, transforming bribes into legally-issued tickets.
The city budget comes to 750bn riyals (pounds 163.4m), which includes funds for schools, health clinics and police departments. He contends that an American trade embargo will not harm Tehran but international bankers predict that the government's efforts to peg the riyal at 3,000 to the dollar are already eating away at Iran's foreign currency reserves.
Further inflation would mean less public spending on the capital, less fresh water for the poor, a dirtier city, more slum housing. In these circumstances, Mr Karbaschi's Islamic philosophy will be sorely tested to keep the hyacinths in his office blooming.Reuse content