Valmiki Ramayana Kishkindha Kanda Sarga 41 Shloka 36
Original Shlokaतत्र योजनविस्तारमुच्छ्रितं दशयोजनम्।।4.41.36।। शरणं काञ्चनं दिव्यं नानारत्नविभूषितम्।
1 source checked for this shloka
तत्र there, योजनविस्तारम् a yojana in breadth, दशयोजनम् ten yojanas, उच्छ्रितम् tall, दिव्यम् wonderful, नानारत्नविभूषितम् adorned with many gems, काञ्चनम् gold, शरणम् dwelling.
'The hermitage of Agastya is one yojana in breadth and ten yojanas in height. It is wonderful, built of gold and adorned with many gems.