འཕགས་པ་ཟ་མ་ཏག་བཀད་པ་ཞས་བྱ་བ་ཐག་པ་ཆན་པའ་མད notes.104

notes.104

104. In Indian literature such as the Pūraṇas, those beings that do not produce descendants are reborn in a realm where the inhabitants continually hang upside down. The seven underworlds, called patala, include realms made of gold. The implication here is that Avalokiteśvara is traveling through the underworlds, one of which is ruled by Bali, which this sūtra describes as being made of iron. The hells and the preta realm are also located below the ground.