Valleys are low areas between mountains, hills, or elevated plateaus. Valleys may contain rivers and lakes due to streams that feed from the higher terrain. There may be waterfalls. There may be floodplains of mountain rivers and contain fertile ground. There may be windmills. Valleys may be surrounded by steep cliffs and there may be cliffside paths. The only way in or out may be by mountain pass. Valleys may be hidden valleys, or mountain valleys.