In order to obtain the Athmalinga of Lord Shiva, Ravana performed severe penance at Kailasa and secured the Athmalinga. The Suras frightened by this, approached Lord Ganesha and prayed to Him, to retain the Athmalinga at Gokarna. As the abode of the one and only one Athmalinga of Lord Shiva, Gokarna gained world wide spiritual significance. This holy place is known as Bhookailasa and the Southern Varanasi. (Ref. Skandha Purana, Guru charitra)