The red colour means show cave. Other cave Caves are natural voids undergoud, large enough to be visited by humans. Special caves, very famous caves, which are not open to the public. They are described for completeness, and to warn people about visiting them. The symbol I used, is the Greek letter Omega, which is often used as a symbol for cave on maps, mainly because it looks like the portal of a cave.
Underground voids are always a place where ground water is collected.
The biggest springs on Earth are always Karst springs, waterfilled caves reaching the surface. The symbol I used, is a blue dot, which is often used as a symbol for springs on maps. Karst feature Karst is a geologic phenomenon which is responsible for most caves of the world. Beneath the caves there are other interesting geologic structures, like sinkholes and loosing streams. The symbol I used, is a circle with centric lines, which is often used as a symbol for small depressions, often sinkholes, on maps.