Man-made, plastic, fluid; the versatility of reinforced concrete is most evident when the structural system is demonstrated openly and the finish and methods of its construction are articulated on its finished surfaces. Architecture’s greatest buildings are a result of the celebration of these properties. Spatial qualities are achieved by pushing the boundaries of structure thus testing our perception of materiality and gravity. Like an arch’s powerful aesthetic in its simplicity and clarity of purpose, the malleability of concrete and its ability to take on plastic form was an ideal material used to by these great architectural masters when testing out new forms and methods. The other dimension to the character of a space lies in the quality of its natural light. Achieving balance and harmony through the graduation of the light appropriate to the function and spatial requirements was a desired goal for builders and architects throughout time. The mood of space is delivered by quantitative aspects such as  intensity, direction and color of light. The qualitative atmosphere draws an emotional, spiritual response as temperature, radiance, reflection and refraction. These signature buildings were realized by the architects’ ability and in depth understanding of structural principals and construction methods specific to concrete that create an object or space. But it is insights into the human, emotional reaction to these spaces achieved by controlling proportions,materials and most important light that transformed these static objects into inspirational spaces.