Pura Ulun Danu Batur, or Pura Bat is one of the two most important temples in Bali, the other being Pura Ulun Danu Bratan, or Pura Bratan. The temple is located at the rim of Lake Batur, a crater lake flanking Mount Batur, an active volcano. The significance of the lake lies in that it provides fresh water to the majority of the rice irrigation system of Bali. Pura Batur belongs to the supreme water goddess, Dewi Danu, who the traditional Hindu Balinese, who call their religion Agama Tirta, or "Religion of the Water", believe makes the water flow into the rivers and irrigation systems.