nagair bhogavatim iva
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
As Bhogavati, the capital of Nagaloka, is protected by the Nagas, so was Dvaraka protected by the descendants of Vrsni — Bhoja, Madhu, Dasarha, Arha, Kukura, Andhaka, etc. — who were as strong as Lord Krsna.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
The Nagaloka 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 Nagas (celestial serpents), and it is said that there are beautiful gardens, rivulets, etc., for the enjoyment of the Nagas. It is understood here also that the place is well protected by the inhabitants. So also the city of Dvaraka was well protected by the descendants of Vrsni, who were as powerful as the Lord, insofar as He manifested His strength upon this earth.