Canto 3 -
Araṇya-kāṇḍa
Chapter 38: Mārīca Instructs Rāvaṇa
Text 3.38.25

हर्म्यप्रासादसम्बाधां नानारत्नविभूषिताम्।
द्रक्ष्यसि त्वं पुरीं लङ्कां विनष्टां मैथिलीकृते॥

harmya-prāsāda-sambādhāṁ nānā-ratna-vibhūṣitām
drakṣyasi tvaṁ purīṁ laṅkāṁ vinaṣṭāṁ maithilī-kṛte

harmya-prāsāda-sambādhām = which is crowded with mansions and palaces 1; nānā-ratna-vibhūṣitām = and which is decorated with a variety of jewels; drakṣyasi = will see; tvam = you; purīm =  the city; laṅkām = of Laṅkā; vinaṣṭām = destroyed; maithilī-kṛte = for the sake of Maithilī.

You will see the city of Laṅkā, which is crowded with mansions and palaces and which is decorated with a variety of jewels, destroyed for the sake of Maithilī.

Nānā-ratna-vibhūṣitām indicates that the gateways in the houses and so on were decorated with a variety of jewels.

Intending to point out that because of Rāvaṇa’s fault, all rākṣasas will be destroyed, Mārīca states in the next verse that the root cause [of that destruction] was association with the wicked.1

1 Because the rākṣasas had associated with Rāvaṇa, they would have to suffer because of his fault. Rāmāyaṇa-bhūṣaṇa: asat-saṅga-doṣa-nyāyārūḍham upavarṇayati akurvanto ’pīti.