Jagoe Dzong is located at Gangyul village under Lingzhi Drungkhag (sub-district).
In 1224, at the age of 40, Phajo Drukgom Zhigpo left for Bhutan to carry out the prophecy of Tsangpa Gyare who has instructed Onrey Dharma Singye to let Phajo travel to Bhutan at an appropriate time.
At the time of Phajo’s arrival at Lingzhi, in Bhutan, a cow belonging to a local rich man named Matong Gyi, had given birth to a calf with the head of a donkey and a snake as the tail. He approached Phajo for help. Phajo subjugated the evil spirit and it became a normal calf. All the nomads of Lingzhi joined together and offered Jagoe Dzong and all the surrounding land to Phajo.
Source and more details at: http://www.wikiwand.com/en/Phajo_Drugom_Zhigpo
