Is this a shelter or explosives store room ?

Got some debate going on with a mate,he says its a shelter i am not so sure,it looks very strong and expensive for a shelter. This is the only shelter in the area ov the pit (just the 1?)I Looked all over net and cant see anything like it,hope you can help.

Front door.
1/2 steel rivited plate.Note the 3 beam/rail track shaped holes on front ?



3 Layers ov brick outside then coverd in earth.



Inside window at other end ?



Room is about 10ft x 6ft,about 6ft high in middle.Steel bands with concrete sections.



Window form the outside.





Thanks for looking.Any help would b good