A city in the Hollow World - this is the deepest point anyone from the Commonwealth has ever been. This is a bit of a disjointed place - non-violent prisoners are allowed to go here and be settlers, though it is worth mentioning there is a prison complex and they are still prisoners. There is an area of non-criminal settlers, and then the prisoners + their keepers, and the two are a bit divided and disjointed in this way.
This is where we heard Kovar Anranios was being kept prisoner, as well as a possible place Emer Kaine might be.