Light concrete slabs or bricks are manufactured as precast concrete. The material is generally from about 95% fine-grained concrete and 5% light-conducting fibers which are placed in parallel layers in the liquid concrete. Thousands of light-conducting fibers are thus embedded in any light concrete element. If they are illuminated from the opposite side (by sunlight or artificial light sources), they direct the light across the material and bring it to “lights”. Thus, no real transparency is achieved, but rather a “copy” means a person or object between the light source and the light concrete are emerging depending on the distance more or less sharp shadows.