Sequestered at the foot of the Yunlong Peak of the Cangshan Mountain, the Butterfly Spring is actually a pool four metres deep and 20 square metres wide. 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, and swarms of butterflies in twenty or so breeds descend on the tree, linking themselves head against tail into numerous coloured 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.