The commemorative monument in memory of the victims who suffered the brutal terrorist attacks on 11 March 2004 is situated on the roundabout near the entrance to the suburban train station, upon a room situated in the vestibule.

The monument has been defined as an answer to the transparency and permeability looked for. It is composed of two areas which are intimately and complementarily linked. Firstly, the exterior is made of glass and secondly the room below ground level from where you may observe the monument.

The sculpture is made of two different layers. The exterior layer which is made of glass blocks and the internal layer which is composed of an ETFE membrane, on which written messages have been printed, from the days consecutive to 11 March 2004.

The glass-like structure is closed and watertight and weighs around 120 tonnes. It is totally transparent and colorless. The blocks are fixed together employing an acrylic glue which sets with ultraviolet light. The absence of opacity in the monument is the key to its conception. Only gleams, reflections and light materially form the monument.

The ETFE membrane is situated in the interior of the monument and is supported by the vacuum created between the monument itself and the membrane; hence it is therefore stable without any opaque support element. The message may be seen through the glass cladding during the day and in a different way at night. The transparent membrane begins in the interior of the vestibule room to reach the visitors of the aforementioned.

The monument rests upon a solid 18.90x17.10m pre-tensed 0.75 deep slab. The works began with the demolition of the existing roof covering. The new slab was supported on existing 0.60m thick walls, which clearly shows that the slab is one-way. The pre-tensioning of the slab is parallel to the working of the slab and is composed of a series of 21 and 19 strand cables with a 150mm2 area.

The access to the room is situated inside the main vestibule of Atocha Station. It is so arranged as to ‘disappear’ so that the light is the main player, that it is an area colored blue and that the only distraction is the window which allows one to see the dome from inside. Everything else is thought and materialized in reference to this single vision. From inside the room one may see the RENFE station without hearing what is taking place there, due to its sound insulation. It is an empty space, silent and with only the light as its main protagonist.