The Pothigai Hills, also known as the Shiva Jothi Parvath, Agasthiyar Mountain, Southern Kailash is a 1,866-metre (6,122 ft)-tall peak within Kalakkad Mundanthurai Tiger Reserve, Tamil Nadu is in the southern part of the Western Ghats of South India. However, peak lies in the border of Kerala and Tamil Nadu.. Ancient tradition holds the mountains of Pothigai to be where the sage Agastya provided the first grammar for the Tamil language. This grammar was further fine-tuned by one of his disciples in the Tolkāppiyam.