Each has a height of 7 metres and a diameter of 30 metres. They are voids rather than objects, things to be experienced rather than seen. You may indeed not be overwhelmingly excited by the photographs on this page, as the Tanks are hard to capture with a lens.
The Tanks at Tate Modern are a work of uncovering as much as addition, and finding rather than making, and there is not much chance that they will imprint their image on the world's imagination. The stadium set out to be a modern Eiffel Tower and succeeded, impressing its image on global television audiences of billions: of all the attention-seeking buildings of recent years, it commanded as much attention as any. This project is by the Basel-based firm of Herzog & de Meuron, architects of that icon of icons, the stadium built for the 2008 Beijing Olympics – or Bird's Nest, as the architects don't like it to be called. This is the conversion of the oil tanks of the former Bankside power station in London – a clover of three buried concrete cylinders – into new spaces for performance and exhibition for Tate Modern, which is what the power station became in 2000. When the dust settles on this year of spectacle and recession-proof Olympic construction, of teetering steel pointing to the sky, of swinging cranes, mayoral openings and breathless press releases, of the mighty Shard and the risible Orbit, one of the most memorable works will turn out to be something invisible above ground, and largely the creation of little-known 1950s engineers.