SB 5.16.2
tatrapi priyavrata-ratha-carana-parikhataih saptabhih sapta sindhava upaklpta yata etasyah sapta-dvipa-visesa-
vikalpas tvaya bhagavan khalu sucita etad evakhilam aham manato laksanatas ca sarvam vi-jijñasami.
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
My dear Lord, the rolling wheels of Maharaja Priyavrata’s chariot created seven ditches, in which the seven oceans came into existence. Because of these seven oceans, Bhu-mandala is divided into seven islands. You have given a very general description of their measurement, names and characteristics. Now I wish to know of them in detail. Kindly fulfill my desire.