Matsya Purana — Design and Splendour of Tripura: Maya’s Threefold Moving Fortress
इत्येवं मानसं तत्राकल्पयत्पुरकल्पवित् मयेन तत्पुरं सृष्टं त्रिपुरं त्विति नः श्रुतम् //
ityevaṃ mānasaṃ tatrākalpayatpurakalpavit mayena tatpuraṃ sṛṣṭaṃ tripuraṃ tviti naḥ śrutam //
Thus, there the knower of city-planning conceived it in his mind; by Māyā that city was fashioned—this is what we have heard—hence it is called Tripura, the “threefold city.”
This verse is about creation-by-design: a city is first conceived mentally by a master of purakalpa and then constructed by Maya; it does not describe Pralaya directly.
It underscores the ideal that settlements and forts should be planned by competent experts (purakalpavit), implying that a king should employ proper knowledge and skilled artisans when founding cities and defenses.
It highlights a core Vastuvidya principle: mental conception (mānasa-kalpanā) and codified planning (purakalpa) precede physical construction—here exemplified through Maya building the famed Tripura.