Gabion: Will Alsop Underground 1/3

When Will Alsop first designed his Jubilee Line underground station in North Greenwich, there were two things he did not expect. He did not expect to have a Norman Foster bus interchange dropped on top of it: and he did not expect the world's biggest circus tent, in the shape of Richard Rogers' Millennium Dome, to land alongside. Still, these things happen. At any moment - possibly tomorrow, possibly even before you read this, so coy is London Underground about its much-delayed project - the station opens, along with the first stretch of the new tube down from Stratford. Which means the whole Dome business is finally entering the realm of reality.

When the firm of Alsop, Lyall and Stormer landed the station job back in the early 1990s, the idea was that it would be buried beneath a gargantuan docklands-style redevelopment. Then came the Dome, and the rapid re-planning of the area led to Foster's surface interchange, perched like a gull's wing over one end of Alsop's buried box. The Dome mushroomed a few yards away, and a canopied boulevard will connect the two. Assuming the engineers get the other end of the line sorted out in time, millions of people will experience Alsop's station en route for the New Millennium Experience next year.

Although it began life in a different world, this palatial, ultramarine blue subterranean space with its leaning mosaic columns and dramatically suspended concourse is the perfect introduction to the architectural sequence that follows. This is no hole-in-the-corner tube station: it is the biggest on the new line, the biggest in Europe. The tower of Canary Wharf would easily fit on its side inside it, with room for quite a few other buildings as well. It optimistically anticipates becoming an interchange for a further tube extension down into the Royal Docks, and is sized to suit.