The Chicago Tunnel Company Railroad Map:

[photopress:Chiacgo_Railroad_Tunnel_courtesy_Phil_Okeefe.jpg,full,centered]

Apparently the system, as it evolved, had many surplus tunnels. And a parcel delivery system that never quite caught on. Seems well-suited for moving food, medicine and people in emergencies. (We haven’t learned yet anything about the flood-resistance of these tunnels, which were, on average, about 40 feet under street level.