City of London tall office buildings including the 600-foot (183 m), 47-storey Natwest Tower, the first skyscraper in the UK. Office space development has intensified especially in the central, northern and eastern parts, with skyscrapers including 30 St. Mary Axe ("the Gherkin"'), Leadenhall Building ("the Cheesegrater"), 20 Fenchurch Street ("the Walkie-Talkie"), the Broadgate Tower and the Heron Tower, the tallest in the City. Another skyscraper, 22 Bishopsgate, is under construction. The main residential section of the City today is the Barbican Estate, constructed between 1965 and 1976. The Museum of London is based there, as are a number of other services provided by
30 St Mary Axe for sale with a price tag of £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 £630 million, making it Britain's most expensive office building. Swiss Re booked a gain of more than £300 million from the sale. The new owners are seeking compensation from four of their former managers on the deal, in which about £620 million was paid for a building with a build cost of about £200 million,