30 St Mary Axe is a building in the City of London, London, United Kingdom, popularly known as the "Gherkin". The site of the building was, until 1992, the location of the Baltic Exchange building. On April 10, 1992 the IRA detonated a bomb close to the Exchange, almost completely destroying it and severely damaging buildings close by.

Following the detonation of the IRA bomb, English Heritage and the Corporation of London insisted that any redevelopment on the site must restore the building's facade onto St Mary Axe and the highly decorated Exchange Hall (formerly the trading floor of the exchange). The Baltic Exchange was unable to meet the financial requirements of such a development and the site was sold to Trafalgar House in 1995. Most of the remaining structures on the site were then carefully dismantled whilst the interior of Exchange Hall and the facade were preserved and sealed from the elements. Later assessment by English Heritage determined that the damage was far more severe than had previously been thought, and they dropped their insistence on restoration, a decision that led to much controversy.

Trafalgar House originally submitted plans for a 1,200 ft tower building with a public viewing platform at exactly 1,000 feet and more than 1m sq ft of office space. However this version of the plan was notable mainly for its highly unorthodox floorplan, which somewhat resembled a slice of gherkin (at least in the minds of sub-editors at The Guardian newspaper, who coined the term). Although this plan was abandoned the nickname has stuck. As well as its popular name of 'the Gherkin', it has also apparently been called 'the Erotic Gherkin' (the original Guardian coinage), 'the Crystal Phallus' and 'the Towering Innuendo' despite resembling neither a gherkin nor a penis.

On August 23, 2000, the Deputy Prime Minister John Prescott, granted planning permission to build a much larger building on the site. The new building was completed in 2004, opening on April 28, and was designed by the architects Foster and Partners . Its unusual cone-like shape is designed so that wind will pass easily around the building. The primary occupant of the building is Swiss Re reinsurers which leads to the building's other common name, the Swiss Re Tower. 30 St Mary Axe won the RIBA Stirling Prize for the best new building by a RIBA architect in 2004. It was the first time that the prize jury were unanimous in their decision.

The building uses several methods to make it more environmentally sound than a typical skyscraper. It uses 50% of the power of a comparable tower. This is achieved through a natural ventilation system which uses thermal effects to drive air circulation through the outer sheath of the tower, which is in effect giant double glazing. Double glazing in houses is limited in thickness to avoid convection of heat; in the Swiss Re tower, this effect is exploited. This cools in the summer, and can be regulated to warm in the winter through passive solar heating. Sunlight is reflected down through the tower, making the working environment more pleasing, and keeping lighting costs down.

Despite its overall curved glass shape, all the panes of glass are flat, with the sole exception of one - the lens-shaped cap at the very top.

See also

• Tall buildings in London
• List of buildings

References

• Campaign to save the old Baltic Exchange, before the start of construction.

External links

• Official homepage
• Structurae: 30 Saint Mary Axe
• Skyscrapernews.com file on 30 St Mary's Axe