New construction techniques using steel, concrete and glass allowed buildings to benefit from natural light, and at night they were illuminated by light coming out through large windows. Today, artificial illumination is also a principal element for shop windows and advertising boards. One of the determining reasos for this progressive conquering of urban spaces throughout the 20th century has, without doubt, been the development of the communication era. Urban areas became endless screens for either projecting combiations of lights created as artistic concepts, or for illuminating exernal elements.