Big Ben is a tower clock famous for its accuracy and for its massive bell. Strictly speaking, the name refers to only the great hour bell, which weighs 15.1 tons, but it is commonly associated with the whole clock tower at the northern end of the Houses of Parliament, in the London borough of Westminster. The tower itself was formally known as St. Stephen’s Tower until 2012, when it was renamed Elizabeth Tower on the occasion of Elizabeth II’s Diamond Jubilee, celebrating 60 years on the British throne.

Source: Britannica