30 St Mary Axe to flight paths for both London City and London Heathrow airports; the revised plan for a lower tower was accepted. The tower's topmost panoramic dome, known as the "lens", recalls the iconic glass dome that covered part of the ground floor of the Baltic Exchange and much of which is now displayed at the National Maritime Museum. "The Gherkin" nickname was applied to the current building at least as long ago as 1999, referring to that plan's highly unorthodox layout and appearance. On 23 August 2000, Deputy Prime Minister John Prescott granted planning permission to construct a building much larger
30 St Mary Axe of the building during the summer and warm the building in the winter using passive solar heating. The shafts also allow sunlight to pass through the building, making the work environment more pleasing, and keeping the lighting costs down. The primary methods for controlling wind-excited sways are to increase the stiffness, or increase damping with tuned/active mass dampers. To a design by Arup, its fully triangulated perimeter structure makes the building rigid enough without any extra reinforcements. Despite its overall curved glass shape, there is only one piece of curved glass on the building, the lens-shaped cap at the apex.