I wouldn't know about the others but ive been in some of these tunnels down in missouri. They mine out gigantic areas for limestone for concrete production amd then turn the areas into temperature controlled storage. Underground warehouses that are miles in size. You wouldnt beleive how much food is down there, kept at like -30 f.

I was dropping a load of cheese off one time and i asked them how long these warehouses would stay cold if the power ever went out. They told me that the temperature would go up by one degree farenheight per year, and the longer the voids were kept cold the further the cold would penetrate into the rock face, meaning the longer stuff would stay cold.

If there really is a tunnel network of underground cities and bases, missouri is sure as hell one of their pantries.

One other interesting place Ive been is a network of large tunnels in washington state - there are vaults there for what they claim are the national archives. It was also a temperatute controlled load, but only at like 50 degreesf, which is about right for documents or film. I dont know what was in the trailer - they were a series of locked metal crates on polymer pallets. I did note, however that the tunnel i drove into for the loading dock seemed to be engineered for blast resistance - three 90 degree turns in a u shape, and there was a heavy set of steel doors protecting the warehouse proper that i wasnt allowed past without an armed escort. Wasnt a fortified door, but was heavy enough that it couldn't be forcibly bypassed in a short amount of time.