> OTOH roads here may be 3 or even 4 levels high at the same point

And here I thought Chicago was complex with lower lower Wacker (just 3 levels).

> GPS is sometimes way off in canyons between skyscrapers

This is probably very challenging for human drivers using navigation, but probably no nearly as much of a problem for a Waymo car with onboard 3D maps of the entire operating area.