Man falls through sidewalk

I always avoid metal grates in sidewalks as they have been known to fail and usually those ventilation shafts they cover can be several stories deep.

Why tempt fate?
 
That wasn’t a metal grate though. It was concrete.

I know, thats even stranger.

But the metal grates you can see and there's been at least 2 that I can recall failing in Toronto and people falling.

Its really bad because you're not expecting it. Everyone has had the instance of climbing down a set of stairs and you think you're at the level of the basement floor and there's one more step that for whatever reason you did not process and you almost break your ankle.

Now imagine 12 feet.