The library is located on the corner of Valldonzella and Montalegre streets, in Barcelona, and occupies a surface area of 2.365 m2. This is a facility in which technology defines the building design, as well as the multiple services it offers. Its location is the result of the special circumstances and particularities of the place and a general analysis of the geometries of the main facilities in that area. The surface area above ground of 1.500 m2 seems to be small for such a large volume; this is why the building does not occupy the whole four floors. The interior space is organized in two structural bays parallel to the square façade. The bay facing the entrance occupies the four floors, and there is a fifth floor set aside for the air-conditioning on the roof. The bay facing the Torres Clavé Garden is thought as a whole space made of four levels, where reading rooms are alternatively placed as trays. The square façade is a two-leaf crystal surface: the external crystal contains a metal fabric made of brass and copper threads that reduce 50% of sun radiation and returns golden reflections that change according to the sun position. The interior side, made of translucent crystal, diffuses sunlight and avoids annoying shades when reading. The columns placed within the double skin and between the bookshelves highlight the floating effect of the reading rooms. To complete this interior space there is the transparent façade facing the south-east, to frame the Santa Magdalena church views.