What features of the prison result in Olivia's pronouncement of the place as a "hell" (100)?

When Olivia calls Colva Prison a "hell" (100), she cites several reasons for her conclusion. She says that it is incredibly hot within the prison, that prisoners are living inside cages like one would find "in an old-fashioned zoo" (101), that there are children imprisoned inside the cages, and that the prison appears to be severely overcrowded.