While towers tall enough for line of sight is ideal, microwave communication can also occur with what is called Tropospheric Scatter. This is a propagation mode where signals are transmitted above the horizon of the receiving station. Some of the energy is reflected by water vapor back to the receiving station completing the link. Troposcatter links can work for a few hundred miles and used to link remote communities such as Nome, Alaska. A troposcatter link was also used to connect West Berlin to West Germany during the cold war since cables could not be laid on East German Territory.