Prehistoric men didn't live in houses, like we do. They lived in caves, which are like holes in the Earth. They are found all over our planet. Caves have also been cut into the softer rocks as well, but these are not prehistoric coves. Natural caves were formed differently. In certain places they were formed by the force of the ocean waves on the coast. Huge pockets of gas in volcanic magma have become caves once the magma solidified. In general, most caves were formed by the force of water wearing the rock away.

How does water cause this? To start with, the rock must be soft, like chalk which breaks up easily. In the same way, the water must have specific qualities. It must be rich in carbonic acid to wear away the calk. Eventually the water evaporates and the calcium is deposited on the ceiling of the cave in candle like forms (called stalactites). Other 'candles' are formed on the floor, where drops of calcium fell. These are called stalagmites.