Big Ben is the long-established nickname given to the tower of the clock at the north end of the Palace of Westminster, where the Houses of Parliament are situated. By extension, the name Big Ben is generally applied to the clock and the tower as well as the bell. The sight of the clock and the sound of its chimes are iconic symbols. On Remembrance Day the chimes mark the 11th hour of the 11th day of the 11th month at the start of the two minutes' silence, and at New Year Big Ben is the focus of the celebrations as the people of Britain tune in their radio or TV stations to hear the chimes at midnight that bring in the new year.
And here, viewed from south of the river at Westminster, Big Ben strikes midnight.