Thirunelli Temple is situated at Vayanad District (Kerala India).
Papanasini Emanating from the heart of Brahmagiri flowing through roots, leaves and flowers of ancient trees and medicinal herbs, Papanasini is a holy mountain stream accessible around 1 km North west of the temple premises. One dip in the cold Papanasini waters in reputed to wash away all sins committed in a lifetime. It is further believed that Papanasini is the confluence of river Ganga and Saraswathy.
You can read more about the temple here and here.
You can see a 360 Degree view of the temple and surrounding here
I have visited the temple twice and the below photos are from that temple and surroundings