It is tempting to call this page "Underground" but since the nearest ground was 40km away that does not seem appropriate.
Underneath the surface there were a few tunnels. These pictures are from the main tunnel, which ran between the ACB & ICB. This transported water & power to the ICB. The sewage all ended up in a chamber off this tunnel - this organic product actually heated the tunnel up to about -12C, the rest of the tunnels were a constant -18C. This is the natural temperature. Only the air near the surface was really cold, a few metres below or above the surface the temperature generally rose. The other tunnels were one for the Meteorological helium supply and one for the SSB utilities (a smaller version of the main tunnel)
These are the flubbers. They are used to store AVTUR for the generators and only need filling a couple of times a year. We pumped sledge loads of fuel from barrels on the surface into the flubbers, which would then last a few months before the next refill. Careful planning meant that we did not need to top them up in the dark
This picture is looking down on the melt tank. This was used to melt snow to provide our hot water. The heat came from the generator exhaust, so when we filled the melt tank with snow there was slightly less heat available to heat the building.