But what will happen inside it? We know that people such as the impresario, Sir Cameron Mackintosh, are involved in what might be called the "spectacular" element of what happens in a central stadium in the middle of the drum, and that there will be other elements in the doughnut around it. But what we don't know - and more important what they don't yet know - is what will be the Big Idea to underlie it.
Visually, both the physical surroundings and the show inside will be wonderful. No doubt about that. Get world-class talent to execute an idea and they will do it wonderfully, stunningly well. But without the intellectual glue of that central idea all that will result is a dazzling, empty, and ultimately useless, mask.
We had been writing along these lines in this paper, and to his considerable credit Peter Mandelson, the minister who has to make the dome work, suggested that if we were so interested we might haul in some people to a meeting where we might hunt the Big Idea. He would start it off. And so last week a group of the most thoughtful people we could collect from all walks of British life found themselves peering across the river from the top of the tower to the site of the dome.
As you might expect not one idea but a host of them emerged - far too many in fact. But there were some common themes which made us realise, I think, that getting this one right was important not just for the Government's reputation, not just for this country, but, if it doesn't sound too portentous, for the world.
To explain: stand back for a moment and ask what is special about this project. For a start the dome is within a couple of hundred yards of the Greenwich meridian, the single most important focal point in time for the start of the next millennium - the International Date Line, the other potential start point, wiggles through the Pacific, an awkward spot for a show. London itself is objectively the most international point on earth: the most visited city on earth; the one with the largest number of international air passengers and with the most international phone calls; the one which manages the largest amount of cross-border equities and has the largest foreign exchange market - and so on.
If it is a good place, it is also a good time - not just because of the resonant number of this 2,000th Christian anniversary. It is a good time because at this moment the world, Christian and otherwise, is going through arguably the most rapid period of change in human history. This decade human population is growing faster than at any past period and maybe any future one. Economic power is shifting from the old developed world to the new developing one. There are profound concerns about the pressure that population and economic growth put on the planet's resources. Technology, particularly in communications, is racing forward so that distance, for many activities, has virtually ceased to exist. We are richer than ever before, but that wealth carries high costs - social and environmental - which rightly trouble us.
So if a single big idea emerged it was that this is a special time for humankind - and that one task of the millennium event is to help explain why this particular time is so interesting, so important for the future of our species, so different from any other past period of our history. Explain, yes, but also entertain and enthuse.
So the Millennium Experience has to include an element of futuristic technology, but not the "old" visions of this - space travel and the like. The new technologies which will change the world during the next century will include biotechnology: issues like how the mind works or how drugs change people's behaviour. Do rave-goers understand how recreational drugs work and why they take them?
The social effects of technical change are often even more important than the changes themselves. Look at the way the invention of the car has changed our shopping habits, or the television our leisure time. Just as the inventors of those technologies had no perception of their social impact, so the inventors of the Internet can have little idea of the way it (and its successors) will change the way we will live in another generation's time.
The show will have to acknowledge the damage done to the environment, but it will need to explain that not all environmental change is catastrophic and that in some areas progress has been made in fixing problems. Tiny example: this year sea bass, that fashionable fish of stylish restaurants, have been caught swimming past the millennium site: technology has cleaned up the Thames.
The dome will also have to show awareness of the astonishing internationalisation that has taken place in the world. Ideas now whiz round in milli-seconds; and people whiz round pretty fast too. Divisions have become vertical (between different types of people in one country) rather than horizontal (between similar people in different countries).
Above all, the experience ought to have a moral or even a spiritual dimension. It comes ill from journalists or politicians who vie for the bottom of the league table of public esteem, but clearly people are hunting for something that goes beyond materialism and technology. Yes, the Millennium Show has to be fun; it must not be too earnest, too sure it is right. And of course it has to be for all people, young and old, and rich and poor, Christians and non-Christians, Britons and non-Britons, all races, all beliefs. But also it has to include an element of morality: why are we here and what are our responsibilities to future generations?
And that surely is the Big Idea. The future will have many features about which we should be truly concerned. There will be billions more of us sharing this globe. There will be environmental degradation. There will be grave social problems within otherwise rich countries. But on the other hand there are wonderful opportunities brought about by technology, better education, better communications and by the fact that the entire world is operating on a common economic system. What we must do now is create a future which is more balanced and more humane. If we can do that in the dome then we will have made a really useful start.