this is a picture of an "above ground" bunker in hamburg - converted into a warehouse after the war by putting openings/windows into the sides .
the official capacity was 18,000 people ! but when an airraid was imminent even more people would crowd into it .
i didn't like the above ground bunkers since anti-aircraft guns were placed on top of them making inviting targets .
i preferred simple underground air-raid shelters , allowing one to stick the nose out for a breath of fresh air .
hbg