Thiruvananthapuram: Hidden beneath the bustling heart of the capital city lies an age-old engineering marvel that continues to evoke wonder—a historic subterranean tunnel that carries drinking water to the city. Originating at Jalabhavan in Vellayambalam, the tunnel cuts beneath the Museum–Vellayambalam road, forming a crucial leg of the pipeline network carrying water from the Aruvikkara Dam.

Built in 1928 under the aegis of the Travancore Royal Family and the British Viceroy, the 170-metre-long passage was constructed using traditional surkhi (brick-dust and lime) mortar. Now nearing its centenary, what makes this structure truly remarkable is that it remains fully operational to this day, faithfully channeling water even as heavy traffic rumbles relentlessly overhead day and night.

Step inside, and the chaotic roar of surface traffic fades into absolute silence. Originally designed to supply water to thousands of households, the pipeline relies entirely on the natural pull of gravity. A 22-metre difference in elevation between the Aruvikkara Dam and the Vellayambalam Water Works keeps the water flowing seamlessly.

While water mains across the rest of the city are laid directly beneath the tarmac, this stretch was uniquely encased in an arched masonry tunnel. That it has survived nearly a century without structural damage stands as a striking testament to the brilliance and foresight of early-twentieth-century engineering.