A sound like a million freight trains blasting out of the bowels of the earth, a massive seismic wave smashing into the city's foundations, skyscrapers toppling, death and mayhem on an unimaginable scale.
An earthquake could wreak that kind of damage in the city if we are to believe Epicentre: Hong Kong, a novel by Ian McFeat-Smith, a Hong Kong-based Scottish engineering geologist.
And, McFeat-Smith says, a major quake may well be more likely here than we are led to believe.
The geologist, who works for IMS Tunnel Consultancy, a firm providing services for tunnelling projects, made his case in a novel, he says, because 'it was easier for people to understand the topic, and they could relate to it better'.
He wrote it because he fundamentally disagrees with the government's stance on the possibility of a quake hammering the city.
According to information published by the Civil Engineering and Development Department's geo-technical engineering office, Hong Kong's seismic risk level is low to moderate. 'There is little evidence of significant recent fault activity in Hong Kong, either onshore or offshore,' it reads.