With the newest subway lines open, this beautiful park is now easily accessible. Guilin Park (Osmanthus Woods Park) is an older park in Shanghai. It has many rock gardens, beautiful walled pavillions, and bridges - much like Yu Garden only greener - plus places for the old men to play games, and the youngsters to run.
Admission is free, and the park is generally open from 5am to 9pm.
You are looking for a distinctive rock 'face'. Here you will find the cache!
Note that since Chinese maps use an unusual datum (the Chinese offset), iPhone type devices will typically not correctly show the cache location. Using different maps (such as OpenStreet) may help, but for best results use of an actual GPS device is suggested for this and all Chinese caches.