The Punakha Dzong, also known as Pungtang Dewa chhenbi Phodrang ('the palace of great happiness or bliss') was built in 1637 - 1638 by the 1st Zhabdrung Rinpoche and founder of the Bhutanese state, Ngawang Namgyal (1594 - 1651). It is the second largest and second oldest dzong (fortress) in Bhutan, located at the confluence of the Pho Chhu (father) and Mo Chhu (mother) rivers in the Punakha-Wangdue valley. Punakha Dzong is the administrative centre of Punakha District, and once acted as the administrative centre and the seat of Bhutan's government until 1855, when the capital was moved to Thimphu, though it still acts as the winter capital for the head of the Bhutanese clergy. It houses sacred relics from the southern Drukpa Lineage of the Kagyu school of Tibetan Buddhism.