I know this because I met a lot of them scooting around the Dome on its big preview day last week, wide-eyed with excitement. About 16,000 people were in - half its capacity - and the bustle and noise they generated at last brought the Dome to life. It works. It feels busy, purposeful, it has a pulse. True, the contents of many of the Zones appear vacuous in the extreme if you are a middle-class, reasonably intelligent, slightly world-weary adult as most of we critics are. But we are not the target market. One of the ironies of the Dome is that it was conceived - by middle-class folk like us - not to be an elitist enclave.

Nobody used to worry about condescending to the masses. The Great Exhibition of 1851, and the more parochial Festival of Britain in 1951, were both put together by the Great and Good to show us and the world how awesome Britain was, and how we'd better sit up straight and pay attention, or we'd get a clip round the ear. This time round, it's all a lot more reflective. The Dome is exhibition planning by focus group. Apparently we have been asked what we think about the Millennium, what our hopes and fears are, and these findings have - after years of grinding through committees - resulted in the displays you see inside the Dome. They have been rescued from terminal turgidity by Michael Grade, the man who insisted on Fun when everyone else had forgotten it. We all owe Grade a great deal.

Hence the Robot Zoo and the Ant Colony in the Mind Zone. Hence the seaside fun of "Living Island" which rather successfully disguises its eco-messages about recycling and water pollution in a rip-roaring kiss-me-quick format. Hence the "British Spaceways" dark ride of the Home Planet Zone, where you sit in moving seats to experience blasts of hot air as you pass volcanoes, and icy draughts as you visit the poles. Hence the fact that you clamber around the internal organs of a giant representative human in the Body Zone, or play a huge game of table football in the "Work and Learning" zone (it's about teamwork, stupid).

The only part exempt from Grade's Fun dictum is the Faith Zone - the most difficult of all, over which more hands have been wrung than any other. Surprisingly, this turns out to be a success. Not so much for its espousal of universal brotherhood, or its discussion of death, or its account of 2,000 years of Christianity. No: the success in "Faith" is the central contemplative space by the American Quaker cowboy artist James Turrell - one of his celebrated "sksyscapes", really a chill-out zone. This is unmissable.