Inside the landmark clock tower.
When it was built, Big Ben was the largest clock in the world. Over 150 years later, it's still chiming every hour and letting the people of London know what time it is.
But how exactly does it work? This video from the Science Channel takes us inside the famous tower to see the inner workings:
There are several surprising facts from the video, including that the clock is still hand-cranked, and that it takes an hour and a half to fully wind it up.
Even after more than a century of service, it's still pretty accurate considering its size and age, though it needs an adjustment of about two seconds every week. The clock's maintenance crew frequently check to make sure it's still on time, and occasionally balance the clock's pendulum with a few pennies.
Here's hoping the clock continues to chime away for another 150 years.
Source: Science Channel