The Punakha Dzong, also known as Pungtang Dechen Photrang Dzong, is the administrative centre of Punakha District in Punakha, Bhutan. Constructed by Ngawang Namgyal, 1st Zhabdrung Rinpoche, in 1637 - 38, it is the second oldest and second largest dzong in Bhutan and one of its most majestic structures. The dzong houses the sacred relics of the southern Drukpa Lineage of the Kagyu school of Tibetan Buddhism, including the Rangjung Kasarpani and the sacred remains of Ngawang Namgyal and the terton Pema Lingpa.The Dzong is located at the confluence of the Pho Chhu (father) and Mo Chhu (mother) rivers in the Punakha - Wangdue valley. The source of the Mo chu river is in the northern hills of Lighsi and Laya in Bhutan, and in Tibet. The Po Chu River is fed by glaciers in the Lunana region of the Punakha valley. After the confluence of these two rivers, the main river is known as Puna Tsang chu or Sankosh River and flows down through Wangdue Phodrang, crosses the Bhutan - India border at Kalikhola and eventually meets the Brahmaputra River.