SB 5.20.2
jambudvipo ’yam yavat-pramana-vistaras tavata ksarodadhina parivestito yatha merur jambv-akhyena lavanodadhir api tato dvi-guna-visalena plaksakhyena pariksipto yatha parikha bahyopavanena; plakso jambu-pramano dvipakhyakaro hiranmaya utthito yatragnir upaste sapta-jihvas tasyadhipatih priyavratatmaja idhmajihvah svam dvipam sapta-varsani vibhajya sapta-varsa-namabhya atmajebhya akalayya svayam atma-yogenopararama.
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
As Sumeru Mountain is surrounded by Jambudvipa, Jambudvipa is also surrounded by an ocean of salt water. The breadth of Jambudvipa is 100,000 yojanas [800,000 miles], and the breadth of the saltwater ocean is the same. As a moat around a fort is sometimes surrounded by gardenlike forest, the saltwater ocean surrounding Jambudvipa is itself surrounded by Plaksadvipa. The breadth of Plaksadvipa is twice that of the saltwater ocean — in other words 200,000 yojanas [1,600,000 miles]. On Plaksadvipa there is a tree shining like gold and as tall as the jambu tree on Jambudvipa. At its root is a fire with seven flames. It is because this tree is a plaksa tree that the island is called Plaksadvipa. Plaksadvipa was governed by Idhmajihva, one of the sons of Maharaja Priyavrata. He endowed the seven islands with the names of his seven sons, divided the islands among the sons, and then retired from active life to engage in the devotional service of the Lord.