The citizen app is garbage. Makes a profit off of fear mongering. This is a densely populated place, of course there is going to be at least some crime near you. Ironically, the only time anyone tried to pick-pocket me was in Spain. That said, I hope you have a better time adjusting to Spain than NYC. To each their own.

And when the broken hearted people living in the world without ID
There will be an answer, DMV
For though they may be parted with their document of identity
There will be an answer, DMV

u/allegheny you are like some Weird Al level genius. I May have to record this for posterity.

Could also be plaster and mesh. All the same, takes mounts made for such walls. You can confirm with the super and then ask at a hardware store for mounts rated to go into such materials.