30 St Mary Axe

30 St Mary Axe, also known as the Gherkin and the Swiss Re Building, is a skyscraper in Londons main financial district, the City of London, completed in December 2003 and opened at the end of May 2004. The details of 30 St Mary Axe is explained in world tour guides below. With 40 floors, it is 180 metres or 591 ft tall, and stands on the former site of the Baltic Exchange building, which was severely damaged on 10 April 1992 by the explosion of a bomb placed by the Provisional IRA. After the plans to build the Millennium Tower were dropped, the current building was designed by Norman Foster, his then business partner Ken Shuttleworth and Arup engineers, and was erected by Skanska in 2001–2003.

The building is on the former site of the Baltic Exchange building, the headquarters of a global marketplace for ship sales and shipping information. On 10 April 1992 the Provisional IRA detonated a bomb close to the Exchange, severely damaging the historic Exchange building and neighbouring structures. The UK government's statutory adviser on the historic environment, English Heritage, and the City of London governing body, the City of London Corporation, was keen that any redevelopment must restore the building's old façade onto St Mary Axe. The Exchange Hall was a celebrated fixture of the ship trading company.

23 August 2000, Deputy Prime Minister John Prescott granted planning permission to construct a building much larger than the old Exchange on the site. The site was special because it needed development, was not on any of the sight lines, and it had housed the Baltic Exchange. The plan for the site was to reconstruct the Baltic Exchange. GMW Architects proposed building a new rectangular building surrounding a restored exchange the square shape would have the type of large floor plan that banks liked. Eventually, the planners realised that the exchange was not recoverable, forcing them to relax their building constraints they hinted that an architecturally significant building might pass favourably with city authorities.

The building was constructed by Skanska, completed in December 2003 and opened on 28 April 2004. The primary occupant of the building is Swiss Re, a global reinsurance company, who had the building commissioned as the head office for their UK operation. As owners, their company name lends itself to another nickname for the building, variants on Swiss Re Tower, although this has never been an official title. 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. 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 buildings 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 over long distances from the north, for instance, it can be seen from the M11 motorway some 32 kilometres or 20 miles away, while to the west it can be seen from the statue of George III in Windsor Great Park. The Gherkin can also be seen from the London Eye. On 25 April 2005, the press reported that a glass panel two thirds up the 590 ft or 180 m tower had fallen to the plaza beneath on 18 April. The plaza was sealed off, but the building remained open. A temporary covered walkway, extending across the plaza to the building's reception, was erected to protect visitors. Engineers examined the other 744 glass panels on the building. The cost of repair was covered by main contractor Skanska and curtainwall supplier Schmidlin.

In December 2005, a survey of the world's largest firms of architects published in 2006 BD World Architecture 200 voted the tower as the most admired new building in the world. In September 2006, the building was put up for sale with a price tag of GB£600 million. Potential buyers included British Land, Land Securities, Prudential, ING and the Abu Dhabi royal family. On 21 February 2007, IVG Immobilien AG and UK investment firm Evans Randall completed their joint purchase of the building for GB£630 million, making it Britains most expensive office block.