The "mountains" are actually a series of five marble and limestone formations, which the locals liken to the shape of a dragon at rest. For the Vietnamese, it is a place of significance, which means you are often climbing with loud tour groups who are trying to elbow past you. The hills are interlaced with caves, some of which are important Buddhist sanctuaries. The caves at the Marble Mountains, like so many in the country, served as sanctuaries for the Viet Cong during the Vietnam War. Each peak is named for an element: Hoa Son, or fire; Mo Son, or wood; Kim Son, or gold; and Tho Son, or earth. The highest mountain, Tho Son, is climbable via a series of metal ladders beginning inside the cave and extending to the surface at the top. Ling Ong Pagoda, a shrine within a cave, is a highlight. The quarries in Non Nuoc village, at the bottom of the mountains, are as interesting as the caves are. Fantastic animals and fanciful statues of folk tales and Buddhist figures are carved from the rock. Try to get a good look before you are set upon by flocks of hawkers. What's more, even if you're interested in the items they hawk -- incredibly cheap mortar and pestle sets, some very nice chess sets, turtles, and small animals -- any amount of marble adds considerable weight to luggage. When someone asks, "Is your bag full of rocks," you don't want the answer to be "Yes." You can easily see the mountains as part of your trip en route either to or from Hoi An; most cafe tour buses stop here.