SB 5.16.8
uttarottarenelavrtam nilah svetah srngavan iti trayo ramyaka-hiranmaya-kurunam varsanam maryada-girayah prag-ayata ubhayatah ksarodavadhayo dvi-sahasra-prthava ekaikasah purvasmat purvasmad uttara uttaro dasamsadhikamsena dairghya eva hrasanti.
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Just north of Ilavrta-varsa — and going further northward, one after another — are three mountains named Nila, Sveta and Srngavan. These mark the borders of the three varsas named Ramyaka, Hiranmaya and Kuru and separate them from one another. The width of these mountains is 2,000 yojanas [16,000 miles]. Lengthwise, they extend east and west to the beaches of the ocean of salt water. Going from south to north, the length of each mountain is one tenth that of the previous mountain, but the height of them all is the same.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
In this regard, Madhvacarya quotes the following verses from the Brahmanda Purana:
yatha bhagavate tuktam
bhauvanam kosa-laksanam
tasyavirodhato yojyam
anya-granthantare sthitam
mandode puranam caiva
vyatyasam ksira-sagare
rahu-soma-ravinam ca
mandalad dvi-gunoktitam
vinaiva sarvam unneyam
yojanabhedato ’tra tu
It appears from these verses that aside from the sun and moon, there is an invisible planet called Rahu. The movements of Rahu cause both solar and lunar eclipses. We suggest that the modern expeditions attempting to reach the moon are mistakenly going to Rahu.