The Marble Mountains are a cluster of five hills made from limestone and marble in Da Nang. It's also a well-known pilgrimage site with peaks, caves, tunnels and temples all just waiting to be discovered. Named after the elements metal, wood, water, fire and earth, Marble Mountains exist in a coastal area that is renowned for stone-cutting and sculpture about 9km south of Da Nang.
The caves within the mountains hold many secrets including bullet holes from when troops used to spy on the US soldiers relaxing on My Khe Beach below and buildings standing within the caves and grottoes. There are also Buddhist sanctuaries and places of worship dotted across the mountains which are a much-visited spiritual site. You can even see a special circular cave here. It leads to the summit, where you can enjoy spectacular panoramic views. http://www.vietnam-guide.com/da-nang/marble-mountain.htm