It’s enough of a task to tunnel below a busy city – all that traffic and life going on above the effort.

But what if you have to go so deep, you’re working within reach of a subway system that’s still actively keeping that city moving?

In this special feature for our ongoing Crosstown Progress series, we’ve created a video explainer, to take you underground to the light rail transit (LRT) construction work taking place at the intersection of Eglinton Avenue and Yonge Street.

While every station and stop being worked on by our builders, Crosslinx Transit Solutions (CTS), have their own hurdles, Eglinton Station is a unique engineering wonder. The largest excavated footprint – 269 metres – on the LRT line, it’s being built under the existing Line 1 subway platform. Think of one transit giant, standing on the shoulders of another.

But to see how it’s being done, watch this remarkable breakdown. And don’t be surprised if you find yourself going back to repeat a few sections. Yes – the work is that complex.