Located at the foot of the Yunlong Peak of the Cangshan Mountain, the Butterfly Spring is actually a pool four meters deep. The gnarling boughs of an ancient silk tree stretch over its surface. In the fourth lunar month every year, the tree puts out butterfly-shaped flowers. At that time, swarms of butterflies in twenty or so breed on the tree, linking their heads against tails into numerous colored ribbon-like strings which keep dangling over the pool. For this annual congregation of butterflies, the silk tree and the Butterfly Spring have become a major tourist attraction of the Cangshan Mountain.

    Source: http://www.yunnan.cn/english/content/tc.htm