Conception and design of the facades "Tomorrow Montparnasse" contest in partnership with MAD architect and DGLA. The main concept is to broadcast using a mirror image of the Eiffel Tower on the North-West of the Tower façade, this reflection is calculated precisely.The effect relies on the principles: - of the concave mirror, - the Fresnel lens. The façade has also of complex geometry, form organic, but constructive process simple and adjustable. The double skin allows to modulate the energy performance, without impact on the image of the building. The building project meets requirements of the existing RT and reached the level of energy consumption "BBC refurbishment 2009" (Cep < ARB –40%).Compared to the existing operating costs are reduced by 42.8%.