This temple is one of the 12 'Jyotirlingas' of Lord Shiva. It was founded by Shri Ram. This is one of the biggest and beautiful temples in the world. There are 22 small ponds (kunds) in the temple premises, which have different tastes of water.
Valmiki Ramayana 6/123/19, 20 Manas 6/1/2 to 6/2/3.