30 St Mary Axe (known previously as the Swiss Re Building), informally known as 'The Gherkin', is a commercial skyscraper in London's primary financial district in the City of London. It was completed in December 2003 and opened in April 2004. With 41 floors, it is 180 metres (591 ft) tall and stands on the former sites of the Baltic Exchange and Chamber of Shipping. This site was extensively damaged in 1992 in the Baltic Exchange bombing by a device placed by the Provisional IRA (Irish Republican Army) in St Mary Axe, a narrow street leading north from Leadenhall Street.

After plans to build the 92-storey Millennium Tower were dropped, 30 St Mary Axe was designed by Norman Foster and Arup Group. It was erected by Skanska; construction started in 2001. The building has become a recognisable landmark of London, and it is one of the city's most widely recognised examples of contemporary architecture.

More Info: en.wikipedia.org