I did some volunteer work in my distant youth, more with the intent of putting something distinctive on my CV than on improving the lot of humanity. I once spent three weeks working nights driving an electric buggy around the warren of tunnels underneath a major hospital, towing carts full of all sorts of medical waste, disassembled beds, broken furniture going for repair, boxes of supplies and tons of laundry, etc, from one drop-off point to another. You could go the entire night and only ever meet three people.
Naturally I soon got bored and spent some time exploring the place. In one of the less-travelled tunnels I found myself up against a 10' square blast door, the entrance to the nuclear bunker where the local great and good had no doubt schemed and plotted to gain places in a refuge from which they could later emerge and rebuild civilisation in their image. Given the number of RAF bases in the environs, I did wonder if they'd stopped to think how likely it would be that their refuge would become their tomb, buried under ten floors of collapsed hospital.