[yldstrk]

why is it hollow under the freaking sidewalk?

[GeronL]

erosion from a water leak?

[cableguymn]

Union not my job issues?

[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.

[terycarl]

why is it hollow under the freaking sidewalk?

that's not even a little bit unusual, there is a lot of space there and adjacent buildings are usually free to take advantage of it.....with restrictions of course

[varyouga]

NYC is jam packed with tunnels and vaults. Vaults are portions of a building's basement that extent beneath the sidewalk and sometimes even the street with cars driving over. Some of the structures below your feet might be 200+ years old.

I'm an engineer in NYC and know for a fact certain blocks have completely hallow sidewalks. I've even seen private tunnels constructed across streets. Most likely used to transfer materials between stores or factories to avoid all the traffic above.

The building owner is technically responsible for maintaining or filling in these spaces but it is typically not enforced unless someone gets injured.