30 St Mary Axe - Gherkin

30 St Mary Axe, also known as the Gherkin and formerly the Swiss Re Building, is a skyscraper in London's main financial district, the City of London, completed in December 2003 and opened on 28 April 2004. It is 180 metres (591 ft) tall, with 40 floors. Its construction symbolised the start of a new high-rise construction boom in London. The building's name is its address, St Mary Axe being the street it is on.

The building was designed by Lord Foster, his then partner Ken Shuttleworth,and Arup engineers, and was constructed by Skanska of Sweden in 2001–2003.

The gherkin name dates back to at least 1999, referring to that plan's highly unorthodox layout. Due to the current building's somewhat phallic appearance, other inventive names have also been used for the building, including the Erotic gherkin, the Towering Innuendo, and the Crystal Phallus (also a pun on Crystal Palace).

The building uses energy-saving methods which allow it to use half the power a similar tower would typically consume. Gaps in each floor create six shafts that serve as a natural ventilation system for the entire building even though required firebreaks on every sixth floor interrupt the "chimney." The shafts create a giant double glazing effect; air is sandwiched between two layers of glazing and insulates the office space inside.

Architects limit double glazing in residential houses to avoid the inefficient convection of heat, but the Swiss Re tower exploits this effect. The shafts pull warm air out 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, Swiss Re's fully triangulated perimeter structure makes the building sufficiently stiff 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 very top.

On the building's top level (the 40th floor), there is a bar for tenants and their guests featuring a 360° view of London. A restaurant operates on the 39th floor, and private dining rooms on the 38th.

Whereas most buildings have extensive lift equipment on the roof of the building, this was not possible for the Gherkin since a bar had been planned for the 40th floor. The architects dealt with this by having the main lift only reach the 34th floor, and then having a push-from-below lift to the 39th floor. There is a marble stairwell and a disabled persons' lift which leads the visitor up to the bar in the dome.

The building is visible from a long distance: from the north for instance, it can be seen from the M11 motorway some 20 miles (32 km) away while to the west it can be seen from the statue of George III in Windsor Great Park. The view from the A10 has been obscured by the new buildings on Bishopsgate