I'm just recommending that we should try and understand from the description what is meant by adhastāt sapta bhū-vivarā. In the above statement, adhastāt sapta bhū-vivarā (SB 5.24.7), the word adhastāt ('beneath'), tells us again that these seven (sapta) holes (vivarāḥ) are beneath or below the surface of the Earth (Bhū), not that there are seven layers of globe-like planets orbiting below a so-called Earth globe. Of course, the word adhastāt can also mean 'below' in the sense that the planet Rāhu is beneath the sun planet by 80,000 miles as in the statement: adhastāt savitur yojanāyute svarbhānur (SB 5.24.1). However, the idea that adhastāt means below or within the depths of the Earth itself is confirmed by a further statement from Śukadeva Gosvāmī: eteṣu hi bila-svargeṣu "In these subterranean heavens." (SB 5.24.8) The Sanskrit word bila means a hole, cavity, hollow, opening, pit, etc. A bilāyana, for example is an underground cave. It is another word used by Śukadeva Gosvāmī to describe the first of these seven inhabited places underground or underneath the Earth: "bilāyanaṁ praviṣṭaṁ puruṣaṁ." (SB 5.24.16) "Bilāyana means the abode in the form of holes." (Commentary by Śrīla Śrīdhara Svāmī) "Now the holes are described individually, starting with Atala" (Commentary by Śrī Bhagavatprasādācārya) "Bilāyana = the place of the hole" (Commentary by Yādavārya to SB 5.24.18) (The above translations are from Dānavīr Gosvāmī's edition to the Commentaries on 5th Canto Bhāgavatam Cosmology by Vaiṣṇava Ācāryas.) The word bila has correlative words and names connected to digging or burrowing. A mouse, for example, is called bilakārin because it lives in a hole. A snake or any animal that lives in an underground hole may be called bilavāsinā or bilamgamā indicating it's habitat below the Earth.