The stunning facade of the Athletic Club captures your attention due to its uniqueness, lighting and dimension. The new stadium has gained more capacity, which can now hold 53,000 spectators. With a facade that changes colour by means of an LED system, San Mamés joins the trend of architectural lighting among the new European stadiums. Red, white and blue stand out in a set of lights that also includes the emblem of the Champions League. Additionally, three large screens strategically located on the exterior intensify the lighting of the complex and makes the stadium more visible. The result of the facade is owed to a joint project between the department of textile architecture at IASO and the architect César Azcarate. Due to this synergy of work and knowledge, IASO's technical team made a specific system that helped meet the needs of the project. One of the aspects that IASO was key in helping construct the new stadium was in the design, manufacture and placement of more than 2,700 ETFE strips, distributed throughout five levels. The white sheets, size 5, 40m by 1.20m with double curvature geometry enables the building to naturally ventilate. The specific characteristics of the material ETFE have been essential for it being chosen. Its translucency, durability, strength and lightness are some aspects that have influenced the choice of this material. IASO contributed all their know-how in ETFE to find a balance between the aesthetic needs of architects and the mechanical limits of ETFE. A clean union between frame and membrane was the result of extensive development in a system for sections with "hidden connections". Another key point was the accuracy in the pretensioned ETFE sheets of 250μm at high and low temperatures without producing wrinkles or tensions that were too high for the membrane. Specific tests were conducted in a large climate chamber to reach an appropriate and sustainable balance for all weather situations. Without a doubt the new facade of the San Mamés stadium is a clear example of the many possibilities offered by ETFE for building unique works, particularly for sports stadiums.