Changangkha Lhakhang was founded in the 13th Century by Nyima, one of the sons of Phajo Drugom Zhigpo who first introduced the teachings of the Drukpa Kagyu tradition of Himalayan Buddhism to Bhutan,and who is revered as an emanation of Avalokiteśvara, The main object of reverence in the temple is a huge bronze "self-arisen" statue of the Mahakarunika form of Avalokiteśvara (rang byung thugs rje chen po), which is in a seated posture with eleven heads and multiple arms. This was the personal deity of Phajo. Some claim this statue is "self arisen" or miraculously occurring,while others say it was made by an exceptionally skilled and inspired Newa artisan at the time of the construction of the temple.  

 Changangkha Lhakhang is a compact temple complex located on the tip of a ridge that juts towards central Thimphu from the hills to the east. Founded in the 13th or 14th centuries, it is probably the oldest surviving temple in Thimphu. The main components and foundations of the monastery are extremely old, long predating the unification of Bhutan in the 17th century by Zhabdrung Ngawang Namgyal.The temple is often frequented by parents with small children seeking to obtain blessings from the protective deity of the temple, Genyen Domtsangpa, who is considered to be the birth deity and protector of children born in JDWNRH national referral hospital in Thimphu. 

Source: wikipedia