Why are there giant concrete tunnels in the desert?

"No.  No.  That's too _small."_
Too small to be assessed _visually._  This is why science in general (and physics in particular) continually stresses mathematical skills.  Intuitive conclusions and well _founded_ conclusions can be two _very_ different things.  I mean just consider how huge the Earth appears to us, since we are _on_ it, and then consider how _tiny_ it is compared to the entire, detected _cosmos._  This is a significance that cannot be assessed _visually._  It has to be assessed _mathematically._