The underground Zhanggong Cave lies in the Yufeng Mountain, 22 kilometers northwest of Yixin City.

It is said in legend that Zhang Daolin, originator of the Taoism and Zhang Guolao, one of the immortals in "Eight Immortals Crossing the Sea" had practiced Taoism and lived in seclusion here. Therefore, it is regarded as "A Place of Happiness of Zhanggong".

The entire underground cave, including two parts (the upper and lower) covers 3,000 square meters with a 1,000 meter route of travel. The lower part is a natural hall surrounded by unfathomable sea; the upper part is a Sea King Hall, which resembles a Dragon Palace under the sea. Over 1,500 stone steps link the two parts together. There are another 72 caves of varying sizes--small ones in big ones, all with their own unusual scenes. What a heavenly abode!