Argia is a dark and dingy city hidden deep beneath the ground with no entrance/exit.
Calvino describes Argia as being very tight, so tight that it's unknown if the citizens can move around.
I decided not to make it too close and claustrophobic because, without room to move, the people living here would just die. However, I made the city dank and dirty, surrounded by rocks with no citizens outside to achieve a similar effect.
My favourite of these is definitely 17. I think it represents Calvino's description the best as it looks very dark and dirty with some kind of clutter lining the streets.