Under a Mid-Levels hill where a landslide killed 67 three decades ago is an intricate network of pipes and tunnels.
The elaborate set-up drains away water to prevent the hillside from giving way while ensuring enough water pressure within the mountains to stop surrounding buildings from sinking into the ground.
In a densely populated city that is hemmed in by mountains and sees more than 300 landslides a year, the drainage system is crucial to avoid a repeat of the twin disasters that took down buildings and killed about 140 people in 1972.
In the face of the dark day, the city learned to tame its hillsides using technology that has become a model for hilly nations such as South Korea, the Hong Kong Institution of Engineers says.
These tactics and other feats of engineering will be on show at the Science Museum in Tsim Sha Tsui East from February 18 to March 28 as part of the Technology for Quality Living exhibition.
On display are technologies that work behind the scenes to make lives better.