The Gherkin - or 30 St. Mary Axe, to give it its prosaic official non-title, just the address of the medieval street on which it sits - is a plump, glossy, circular, tapering latticework structure, 180 metres or 590 feet high, rising 40 floors to a 360 degree observation dome on top. This contains a double-decker private bar and restaurant that you will have to know people who know people ever to get to see. A glimpse of the tall ground-floor foyers, clad in shimmering ribbed aluminium, is as much of a sense of the interiors as most people are ever going to get. But that won't stop them trying.

Norman Foster's tower is scarcely completed - builders are still finishing off interiors of the the top levels and the new granite plaza around its base - but it already serves in advertisements and TV programmes as the new symbol of London. Its owner, insurance giant Swiss Re, is inundated with calls from the public desperate to go to the top. Were it to be open to the public, it could easily be as popular a destination as the dome of Foster's Reichstag in Berlin. "We're the developer and tenant of an iconic building that is publicly embraced," said Swiss Re's project director Sara Fox, over a lunch laid out on a table on one of the still-empty floors, the week before the opening. "In a sense people now feel ownership of the building. They're in favour of it, they like to point to it and say - this is my London skyline, now let me in. If we charged as much admission as Disney World, we could probably pay off the cost of this building in a year. But I have to say no. It's an office building, people are working here."