Foster was assigned the brief for a development on the site of the Baltic Exchange in the 1990s. The Exchange was damaged beyond repair by a bomb left by the IRA. Foster + Partners submitted a plan for a 385 metre tall skyscraper, the London Millenium Tower, but its height was seen as excessive for London's skyline. The proposal was scrapped and instead Foster proposed 30 St Mary Axe, "the gherkin" due to its design which alluded to its shape. Foster worked with engineers to integrate complex computer systems with the most basic physical laws, such as convection. Green, sustainable energy ideas include the complex facade which lets in air for passive cooling and vents it as it warms and rises.
Foster's earlier designs reflected a sophisticated, machine-influenced high-tech vision. His style has evolved into a more sharp-edged modernity. In 2004, Foster designed the tallest bridge in the world, the Millau Viaduct in southern France, with the Millau Mayor Jacques Godfrain stating; "The architect, Norman Foster, gave us a model of art."
In January 2007, The Sunday Times reported that Foster had called in Catalyst, a corporate finance house, to find buyers for Foster + Partners. Foster does not intend to retire, but sell his 80–90% holding in the company valued at £300M to £500M.
In 2007, he worked with Philippe Starck and Sir Richard Branson of the Virgin Group for the Virgin Galactic plans.
Foster currently sits on the Board of Trustees at architectural charity Article 25 who design, construct and manage innovative, safe, sustainable buildings in some of the most inhospitable and unstable regions of the world. He has also been on the Board of Trustees of The Architecture Foundation.