Watch Ricky's report
The world's most famous clock is celebrating its 150th birthday.
Big Ben (which is actually the name of the bell inside) forms part of the Palace of Westminster- that's where all the politicians work.
The bell weighs a massive 13.5 tonnes and the clocktower stands 96m tall.
Millions of tourists come to London to see and hear Big Ben, and last year it was voted Britain's favourite attraction in a survey.