Valmiki Ramayana Ayodhya Kanda Sarga 15 Shloka 31
Original Shlokaततो ददर्श रुचिरं कैलासशिखरप्रभम्।।2.15.31।। रामवेश्म सुमन्त्रस्तु शक्रवेश्मसमप्रभम्।
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तत: thereafter, सुमन्त्र: तु Sumantra on his part, कैलासशिखरप्रभम् in lustre comparable to the peak of Kailasa, शक्रवेश्मसमप्रभम् resembling in splendour the abode of Indra, रुचिरम् lovely, रामवेश्म palace of Rama, ददर्श beheld.
Thereafter, Sumantra beheld the beautiful palace of Rama, resembling the abode of Indra or the peak of Kailasa in its splendour.