It is famous primarily for the legend of how it got its name. It is said that once upon a time, the site of the monastery was an extremely deep lake. In the lake, there was a five-headed dragon. After Songtsen Gampo gained control of Tibet, he decided to drain the lake and build a castle in its place. Seven days later, the lake disappeared. To mark this success, some pearls were buried as the cornerstone for the monastery, which is how the monastery got its name.