ST sends me to Rio (via AP) which reports Bar codes on sidewalks give tourist info:

“Rio de Janeiro is mixing technology with tradition to provide tourists information about the city by embedding bar codes into the black and white mosaic sidewalks that are a symbol of the city.”

This might be a solution to improving navigability, though I think it will puzzle archeologists in 1000 years. The problem of course is it makes people look (1) at their phones rather than the city, and (2) at the sidewalk instead of what’s in front of them.