ज्वलनेन burnt, परीतानि by fire, निपेतुः fell down, भवनानि mansions, महागिरेः large mountain, वज्रिवज्रहतानीव burnt by thunderbolt, शिखराणि peaks, यथा that way, महागिरेः like huge mountains.

The mansions burnt by fire fell down like a huge mountain struck by a thunderbolt.