The tower with more names than any other, Swiss Re, the Gherkin, the Towering Innuendo, and officially the rather uncatchy 30 St. Mary's Axe is the tallest building to have been built in the City of London between 1979 and 2004. London's have already taken it into their hearts, whilst it's even won the Stirling RIBA Prize of 2004. Here we take a look at what has fast become a new international icon for Britain's capital city.

History.
The Baltic Exchange was a shipping exchange, founded by the Georgians and one of the major financial buildings of London. Given it's importance, and closeness to the insurance industry it's no coincidence it is literally across the road from Lloyds of London.
In 1992 the IRA set off a massive bomb as John Major was celebrating a Conservative election victory. Damage was widespread and nowhere was it more severe than outside the Baltic Exchange which was almost completely destroyed by the blast.
Like the Luffewaffe before them, the IRA had created an opportunity for a prime spot in the center of London to be redevelope, albeit at a heavy price to those who had died and the destroyed architecture. One thing that isn't realised is how close they had come to actually having caused so much damage that Tower 42 was almost toppled and for a while demolition was seriously considered. This though was not to be and instead redevelopment of the City of London would happen.

Thinking Big.
Realising what they were faced with it was Norman Foster and Partners who first decided this was an excellent position for a new tower. The building plot didn't conflict with any of the precious sight lines that cut up the City to preserve the views of St Pauls.
Perhaps spurred on by the annoyance of the inability to build the Commerzbank HQ in London where it was originally designed for, Foster and Partners came up with a similiar three-sided but more organic looking super-scraper dubbed the Millenium Tower. At approaching 400m tall it completely dwarfed all it's surroundings and with this being the late 90s looked rather out of place compared to the rest of the cluster which was only at a modest height.
The building was proposed and despite its massive size the planning authorities found they had little legal ground on which to oppose the building. In the end it was left to the CAA who ruled that Millenium Tower was so tall it could have planes crashing into it. From then it was back to the drawing board.
The precedent though for developers had been set, to think big for the site.

An Enlightened Client.
The developer SKMC wanted a mixed-use high-rise building for a prime site at the western end of West India Quay. It should be a landmark building with the latest up to date design in a concious contrast to the West India Quay preservation area whilst at the same time respecting its surroundings. A covered amenity space and proper access approaches for pedestrians and cyclists were also required.
The Greater London Authority set four objectives for the site if it was to get the support of the GLA. These were the facilitation of a future Crossrail, contribute to the urban design of the area, an environmentally sustainable building, the tallest structure possible to help cement the Isle of Dogs as a center in London.

Looking to Florence.
This sort of building had been attempted before in a certain sense. True no-one had built an egg that tapered at both the top and bottom but ever since the construction of Florence Cathedral with it's almost impossible dome. Brunelleschi's cupula was completely hollow with the masonry skin being self supporting.
Looking to Florence it is clear that from a design perspective it is more efficient of a building shaped like this to be hollow inside, this meant Foster having to discard the traditional skyscraper core and use the shell of the building to hold itself up instead with only basic support from the inside. Perhaps it was this that first turned Foster and Partners to the cathedral dome.
It's obvious that plenty of inspiration was drawn from this structure, spiralling courses of brickwork forming two light shells were used in the cathedral dome, Swiss RE was clad in a double skinned spiral of glass. As Brunelleschi had found, spiralling skins on structures like this were more effective at supporting the building and controlling the curvature. This was crossed with the lattice-work of Buckminster Fuller, who Norman Foster had worked under when he first joined architecture, to produce the signature cladding we have today.
As with all structures of this shape there are both horizontal and vertical forces as the structure is forced both down and out placing immense stresses on it as the Romans discovered when the dome of the Pantheon started to crack. Brunelleschi controlled these forces by fitting chains between the two skins of his dome to stop it exploding outwards under the strain, with the Gherkin the role of the chains is instead the floors which are latched to the outside of the superstructure to restrain them.

The Aesthetics and Architecture.
Faced with a working massing model for the site, DMWR then had to take into account the actual aesthetic qualities of the building. They plumped for a look that can only be described as 'Thames Gateway'. The similarities between the 11 storey crown of the tower and the Thames Flood Barrier are entirely intentional however it has been trimmed to fit in more with the east west flow of the site.
Looking up at the tower from the ground is supposed resemble a bow of a ship referencing the nautical history of the area to create a highly sculptural building that is a complete contrast to the surrounding functional Canary Wharf towers. It's clean simplicity and glass walls are to contrast purposefully with the podium whilst allowing a stacking of uses on top of each other.
The base of the tower is designed to allow the whole project to fit in at street level. A highly complex base, it will predominantly be a frameless structure of glazing with industrial touches of steel and cabling to remind the public of the nearby dock cranes.
The great majority of the skyscraper will be clad in reflective glass tinted slightly green.
Materials used in the public realm of the tower are designed to reflect the industrial heritage of the site and focus on more traditional building materials, namely granite, steel and timber all set in industrial portions to reflect the size of the development.

Engineering a Tower.
Building a tower is never easy, the higher you get the windier it gets and the more stresses are put on the superstructure that supports it. For a slender tall building like Columbus Tower the most effective way to provide it with the support it needs it by building a concrete core surrounded by a simple metal frame which can provide floor by floor support. A central core is particularly useful when a building is arranged around its center as most traditional skyscrapers are.
This building has a core 9 meters wide and 36 meters long split into five separate sections to provide additional strength.
A special substructure has been designed to allow the proposed Crossrail to travel under the tower without excessive weight placed on the tunnel. In tipping a wink to this the columns of the tower which sit directly over the eastbound tunnel are designed to articulate what is underneath.

Future Prospects.
Having been approved work is expected to start on the site almost immediately. The mixture of office and hotel space combined with the wealth of the investment company involved who seem determing to build speculatively guarantees an early start whilst its height should have hotel groups queuing up for the tallest rooms in London.
Barclays are set to vacate the site in the summer and demolition of such a small building will not take long. By the end of the year the core should have started to rise above the ground creating a new and exciting addition to the Canary Wharf skyline.