The Nāgaloka planet is situated below the earth planet, and it is understood that the sun rays are hampered there. The darkness of the planet is, however, removed by the flashes of the jewels set on the heads of the Nāgas (celestial serpents), and it is said that there are beautiful gardens, rivulets, etc., for the enjoyment of the Nāgas. It is understood here also that the place is well protected by the inhabitants. So also the city of Dvārakā was well protected by the descendants of Vṛṣṇi, who were as powerful as the Lord, insofar as He manifested His strength upon this earth.
Beneath Rasātala is another planetary system, known as Pātāla or Nāgaloka, where there are many demoniac serpents, the masters of Nāgaloka, such as Śaṅkha, Kulika, Mahāśaṅkha, Śveta, Dhanañjaya, Dhṛtarāṣṭra, Śaṅkhacūḍa, Kambala, Aśvatara and Devadatta. The chief among them is Vāsuki. They are all extremely angry, and they have many, many hoods—some snakes five hoods, some seven, some ten, others a hundred and others a thousand. These hoods are bedecked with valuable gems, and the light emanating from the gems illuminates the entire planetary system of bila-svarga. SB 5.24.31