Seven years after a Reddit post resurfaced images of the vast chambers beneath Jurong Island, Singapore’s underground oil storage marvel continues to fascinate people online.

The post described the Jurong Rock Caverns as standing 27 metres high, 20 metres wide and 340 metres long, stretching as deep as 130 metres underground. For many, the dimensions alone were enough to spark disbelief.

But beneath the internet’s renewed curiosity lies one of Singapore’s most ambitious engineering achievements — a hidden world carved into solid rock, built to solve a very real problem above ground: space.

A City Built Downwards

In land-scarce Singapore, every square metre matters. That reality is perhaps nowhere more evident than on Jurong Island, where petrochemical plants, refineries and global energy companies operate side by side. Rather than consume more precious surface land, Singapore chose to go underground.