SB 6.2.31

atha te kva gatāḥ siddhāś
 catvāraś cāru-darśanāḥ
vyāmocayan nīyamānaṁ
 baddhvā pāśair adho bhuvaḥ
Synonyms: 
atha — thereafter; te — those persons; kva — where; gatāḥ — went; siddhāḥ — liberated; catvāraḥ — four personalities; cāru-darśanāḥ — extremely beautiful to see; vyāmocayan — they released; nīyamānam — me, who was being carried away; baddhvā — being arrested; pāśaiḥ — by ropes; adhaḥ bhuvaḥ — downward to the hellish region.
Translation: 
And where have those four liberated and very beautiful persons gone who released me from arrest and saved me from being dragged down to the hellish regions?
Purport: 

As we have learned from the descriptions in the Fifth Canto, the hellish planets are situated in the lower portions of this universe. Therefore they are called adho bhuvaḥ. Ajāmila could understand that the Yamadūtas had come from that region.