Follow the steps behind the Sela Chaitya and you'll drop down to a junction. The right branch here takes you to the Naga Pokuna (Snake Pool), so called because of a five-headed cobra carved in low relief on the rock face of the pool. Its tail is said to reach down to the bottom of the pool. Water from here fed the Sinha Pokuna below.
From here you can descend to the stairway and the second landing. Alternatively, return to the junction and take the path up to Et Vihara.
