[Right Wing Assault]

why is it hollow under the freaking sidewalk?

In older cities, the used to have freight elevators that rose up through double steel doors in the sidewalk. Trucks would drop stuff off, they would put it on the elevator, and shortly it would be in the basement. The doors closed as the elevator went down.

Eventually, a lot of places closed those but there are still a lot around, probably not in use. Eventually, those doors and/or their supports go bad. 400 pounds walks by and - BLAM! Down we go!

Since cities inspect sidewalks, you would expect they would especially look at these.

[Right Wing Assault]

Here are some guys waiting for one to go up or down.

Here's a website with a bunch of pics:

Sidewalk elevator

[GeronL]

interesting