It's among the world's most photographed landmarks, a symbol of the United Kingdom and an engineering marvel.
But London's Big Ben also has an important job to do as it rings in the new year.
Three expert technicians are employed full time to tend to the icon and about 300 mechanical clocks in the adjoining Palace of Westminster.
The ABC was granted access to the tower to see how they've been preparing for December 31.
"Everyone is looking to this clock, to Big Ben, to strike midnight and let us know when New Year's Day has started," says one of the clockmakers, Andrew Strangeway.
"The fireworks are timed to go off with the strike of Big Ben so we have to be on time.
"Last New Year's, in fact, we struck midnight within about five-thousandths of a second of time, which for a 166-year-old clock is pretty good."
Mr Strangeway, 39, is the youngest of Big Ben's clockmakers. His two colleagues are in their 60s.
While the 11-storey, stone-clad tower is often referred to as Big Ben, Mr Strangeway points out it's actually the largest of the bells housed inside it, not the structure itself, that's been given that nickname.
The actual building is officially called Elizabeth Tower, named after the late Queen Elizabeth II during her 2012 Diamond Jubilee year.
Inside the tower, for technicians like Mr Strangeway, ear protection is a must when the bells go bong.
"It reaches somewhere in the region of 110-115 decibels when Big Ben strikes, so ear defenders are a must," he says as the 200-kilogram hammer pulls back to hit the bell.
You can feel the vibrations.
Mr Strangeway is a qualified mathematician who retrained as a clockmaker because he wanted a job where he could work with his hands.
The clock mechanism inside the tower is intricate and pristine.
"It's the clock itself that is going to lift and drop the hammers that ring the bells on the quarters and on the hour, and because they're big bells you need you need a big clock," Mr Strangeway explains.
"The clock has been here since 1859, and it's really the same mechanism that has been here the entire time, so it's working in exactly the same way as it has for over 165 years.
"This was really the height of clock-making in its day. It was a big step forward in accurate public time pieces."
Every Monday, Wednesday and Friday, Mr Strangeway or one of his colleagues ascends the lift and spiral staircase to wind the clock, which is driven by a system of weights.
These days there's also a mobile phone application to assist.
"It's a real privilege to work in this space with this clock. I'm one in a long line of custodians of this clock, and without people looking after it it wouldn't still be here," Mr Strangeway says.
The four clock faces at the top of the tower are made up of more than 300 individual panes of glass in cast iron frames. No two are the same.
Pink Ross is one of the Palace of Westminster's education officers. She's also an Australian who's lived in London for 20 years.
"My heart jumps every time I hear Ben actually bonging," she says.
"It makes me feel like I'm home. I feel like I've got two homes. I've got Australia and I've got London.
"It just gives me goosebumps, I love it. And then we get to see it on New Year's Eve and it just brings the year to an end and it starts a new one. It's a perfect ending and beginning."
Ms Ross will see Big Ben ring in the new year from street level, but Mr Strangeway and his clockmaker colleagues will have a unique observation point: right beside the famous bell.
"Once we've done our bit, once the clock has struck, we can watch the fireworks, and they are just on the other side of the River Thames, and we do get a rather good view of those. Best view in the house," he says.
