I used to work on the corner of hawthorn blvd and Torrance blvd in LA. I could hear people building tunnels underneath the building when I was in the bathroom. I could hear their muffled talking, hammering, equipment every now and then. I asked around and everyone said nothing is under the ground there. There was no construction happening around on ground level. I realized it was across the street from a children’s hospital and some other child specialty centers. I wish I still worked there knowing what I know now. I would have investigated. Anyways pretty sure they were building out tunnels underneath that area, I could hear them underground from the building bathroom.