Matsya Purana — The Cave-Sanctuary: Jewel-Lake
तम् उच्छ्रितम् अथात्यन्तं गम्भीरं परिवर्तुलम् न तत्र सूर्यस्तपति न विराजति चन्द्रमाः //
tam ucchritam athātyantaṃ gambhīraṃ parivartulam na tatra sūryastapati na virājati candramāḥ //
It is described as exceedingly lofty, profoundly deep, and circular in form; there the sun does not burn, and the moon does not shine.
Rather than describing pralaya directly, the verse uses cosmic geography to portray a realm beyond ordinary celestial illumination—suggesting zones of existence where the usual order of sun and moon does not function.
Indirectly, it supports the Purāṇic ethical framework by reminding rulers and householders that worlds of experience can be radically different from human norms—encouraging dharma, restraint, and right conduct to avoid falling into bleak or deprived states.
No direct Vāstu or ritual rule is stated; the main takeaway is symbolic—ritual and sacred architecture often emphasize light (sūrya/candra) as auspicious, and this verse contrasts that with a realm defined by the absence of such illumination.