By CGTN's Lin Nan 

The Customs House clock tower on the Bund is a landmark in Shanghai. The clock's chimes have echoed across the Huangpu River since 1928 and are as integral to the lives of locals as the chimes of Big Ben are to Londoners. Always keeping an eye on the clock is Wei Yunsi, its fourth keeper.

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Climbing 117 steps, this is how Wei's work day has started for the past 27 years. The 58-year-old is the fourth guardian to maintain the clock on top of the Customs House, to ensure it chimes accurately every 15 minutes. 

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“In the past, many locals didn't need a watch to know the time when they came to the Bund. They could estimate the time simply by listening to the length of the clock's chimes. The bell is iconic in many people’s memories here,” said Wei. 

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The clock is the largest in Asia and the third largest in the world after London's Big Ben and the one in the Red Square in Moscow. Compared with his predecessors, Wei’s job has been made easier by some technological innovations. But modern technology doesn't play a role in every part of his work. 

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Over the years, Wei has watched the sweeping changes overtake Shanghai from the top of what was once the city's highest building. Not far from retirement, Wei has high expectations for his successor.

“The clock tower is an icon of Shanghai, and it is a privilege to work here. You need to be very responsible, to balance work and life well, and treat the clock like your child,” he said. 

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Wei hopes to take his family on tourist trips after he retires, but before that, he plans to stick to his post to ensure the clock bell echoes across Shanghai just as it has done since 1928.