ruins are the parts of buildings that are left after they have been destroyed and cannot be used properly any more. many ruins are ancient and famous like the ruins of the forum of ancient rome, or the ruins of tintagel castle on the coast of cornwall. ruins can be caused by wars or by natural disasters such as earthquakes, fires and volcanos. sometimes people leave a house or a village to stand empty, and move somewhere else. when this happens, the house or village slowly becomes a ruin.