For the Habitat II conference, examining the escalating crisis of the world's cities, is the seventh of its kind in just six years and it is hard to find anyone here - including the UN officials who have organised them - who do not believe that, for the time being, enough is enough. Indeed the conference organisers hopefully describe it as "the last UN conference of the 20th Century".
Many are voting with their aeroplane tickets. For the conference is far less well attended than its predecessors - on children, the environment, human rights, population, social development and women - though, arguably, its subject is the most urgent of all.
Billed as the "City Summit", it will, at the latest count, only attract 16 heads of state and government, compared to the 110 who attended the 1992 Earth Summit in Rio, or the 121 who turned up at the Social Summit in Copenhagen a year ago. None of the major Western leaders are expected and few world figures are scheduled to attend, except for Pakistan's Benazir Bhutto. To be fair, the organisers have not tried as hard to attract leaders as at previous summits, but the number of ordinary politicians and officials - and press - also falls well short of expectations. Delegates are outnumbered by security men assigned to protect them.
The issues at stake remain immensely important. Within the next few years humanity, for the first time, will become an urban rather than a rural species, as the world's cities expand to - and beyond - bursting point. As recently as 1975 only a third of the world's people lived in towns and cities; by 2025 nearly two-thirds of a greatly increased population will do so.
The problems addressed by previous conferences are at their most concentrated in cities. The contrast between wealth and poverty is at its most acute, population pressures and social dislocation are at their greatest, and so is the toll on the environment. Already at least half-a-billion people now live in the third world's teeming slums and every day 50,000 people - mainly women and children - die as a result of poor housing, water or sanitation. In both Europe and the US at least three million are homeless.
Yet on Tuesday Jesse Helms, the powerful chairman of the US Senate foreign relations committee, hit out at UN conferences in general and this one in particular. "No American has heard of Habitat II," he told a congressional hearing. "Frankly I doubt that many Americans have even the vaguest notion as to what role, if any, these conferences play in promoting US interests overseas." Their cost, he said, was "exorbitant".
This is a frequent charge from the right, which sees the meetings as expensive boondoggles, producing little but junkets in exotic cities for professional conference-goers.
Habitat is costing the UN only $1.7m (pounds 1.1m ) and none of the others, except for the Rio Summit, has clocked in at more than double that. The host country pays more. Turkey is forking out $90m for Habitat II: but $75m is for facilities it will use again and again - such as a renovated conference centre, and a new telecoms service - and the remaining $15m is being provided by industrial sponsors. In all, the actual figure is lower than the cost of the first Habitat conference in Vancouver 20 years ago, despite inflation.
Delegates spend their time, far into the evening, in airless rooms, endlessly debating wording in tedious documents. One bulky British commentator wrote during last year's social summit that the main attraction for some African delegates was "the cultural excitement of experimenting with lobster crackers" in the quayside restaurants of Copenhagen. In fact the city's restaurateurs complained loudly at the lack of custom from those working late at the conference centre.
The charge of ineffectiveness has some justice. But previous conferences have still produced impressive results. There has been remarkable progress in achieving specific goals for child welfare laid down at Unicef's 1990 summit: it is estimated that so far these are saving the lives of 2.5 million children each year. The Rio Earth Summit, despite being written off by environmental pressure groups, has resulted in four international treaties -on global warming, wild species, fighting the growth of deserts and regulating fisheries - and agreed an agenda of action now being implemented by 1,200 local authorities worldwide.
The conferences also force governments to focus their attention, however briefly, on long-term issues.UN Secretary General Boutros Boutros Ghali says that they are the most effective way the UN has yet found of engaging public opinion behind the "decades of hard work" needed to bring solutions and they have drawn up an agenda for the UN for the next century.
Sir Shridath Ramphal described the conferences as "the high point in our cerebration ... on some of the most critical issues of human survival". But the normally ebullient former Commonwealth secretary general noted that, while history will record that the human species used "its unique power of the mind to think its way to survival", it would not be as positive in recounting what humanity consequently did. Realising how little governments have done following the great conferences, the organisers of Habitat II have deliberately encouraged a less confrontational atmosphere and set a precedent by involving local councils and pressure groups in negotiations. Ismail Serageldin, a vice president of the World Bank, describes this as a "watershed".