A Tunnel Beneath Bengaluru, a 3-Billion-Year-Old Rock at Lalbagh: Can an Ancient Geological Treasure Survive the City’s Growth?

Bengaluru: How old can a rock we casually walk past really be? A hundred years? A thousand? A million?

At Lalbagh, the answer takes us back roughly three billion years.

The Peninsular Gneiss associated with Lalbagh represents a geological history vastly older than human civilisation. Long before modern cities, roads or recorded history, the geological processes that shaped these rocks were already underway.

Now, Bengaluru’s proposed underground tunnel-road project has brought the safety of this ancient geological heritage into public focus.

The Geological Survey of India has raised concerns about potential geological and groundwater impacts associated with the project.

What does three billion years really mean?

Human lives are measured in decades and civilisations in thousands of years. Geological history stretches into billions. The Lalbagh formation is therefore more than a scenic rock — it is a page of Earth’s history preserved in stone.

Why could tunnelling matter?

Building a major tunnel beneath a city can involve deep shafts, tunnel-boring machinery, excavation, vibration and changes in stress within surrounding rock.

One concern is whether construction activity could affect existing natural fractures. That does not automatically mean the formation will be damaged, but the risk needs to be carefully studied before major work proceeds.

There is another issue: groundwater

Groundwater moves through layers of soil, rock and natural fractures. Large underground structures can potentially influence those pathways.

Could tunnelling alter groundwater levels or affect the natural movement of water around Lalbagh? These questions require detailed scientific assessment rather than assumptions.

Does that mean Bengaluru should abandon the tunnel?

Not necessarily. Bengaluru has a genuine mobility problem and needs better transport infrastructure.

The real question is: How can Bengaluru build the infrastructure it needs without unnecessarily damaging natural heritage that cannot be recreated?

A road can be rebuilt. Ancient geology cannot.

A damaged road can be resurfaced and a building can be reconstructed. But humans cannot recreate a geological formation produced by natural processes over billions of years.

The objective should not be to stop development, but to make development smarter, safer and better informed.

Why should Tumakuru care?

Tumakuru is also expanding rapidly. Roads, industrial areas, residential layouts, highways, rail infrastructure and large construction projects will continue to reshape the district.

The Lalbagh debate offers a simple lesson: Before deciding what we build above the ground, we should understand what exists beneath it.

The bigger question

Bengaluru must continue to grow, but a modern city should also know what is worth preserving.

Development is not only about building something new. It is also about knowing what must survive while we move forward.