The secret for the realistic rendering of the concrete lining is the exclusive use of selected genuine cement sands with the addition of polymers in aqueous emulsion, in order to obtain high levels of mechanical resistance to water and abrasion without losing permeability. It is not therefore a resin, but real concrete. Our manufacturing process involves coating the material with a spatula by hand and it is then left to dry naturally. This manufacturing process enhances the chromatic and tactile characteristics, creating appreciated shading of tones and the typical reliefs of concrete on the surface. The concrete finishing is protected by a coat of nano-molecular paint, that protects it from chemical agents, food-borne chemicals in particular.