The position of the Diagonal Zero Zero Tower is exceptional because it is located at the start of the Diagonal, Barcelona’s main avenue, as well as being located on the border of the Forum’s larger areas by the sea. Tailored to house the Telefónica Group's corporate headquarters and its main global R&D departments, it is a contextual building with a symbiotic relationship with the environment. It is a trapezoidal prism, sharp and stylised, light and whitish in colour, which takes advantage of the shape of the solar diamond. Through the extra clear glass of the curtain wall, dynamic volumes that respond to the different specificities of the interior program are revealed, and they are related to the various heights of the nearby buildings. The standard office floors are open, taking advantage of the structural system of the tower: a central core of support and a perimeter structure along the façade allow a floor which has no pillars.

The tower, with the Forum Building, marks the end of Diagonal Avenue. One is vertical and the other is horizontal, forming a complex that complements and serves as a door to what was the site of Forum 2004. It has, against Diagonal Avenue, a very sharp front, pointed diamond, which marks a clean edge about a hundred metres high that starts directly from the ground, without any base.
The façades of the tower are characterised by a network of intertwined crooked columns, called bamboos, which evenly distribute the weight of the building while nuanced by the sun. Due to their apparent simplicity, the façades are very complex.
The ground floor of the building, occupied by the Telefónica company, is public and, just where the building is being sharpened, it is characterised by a nine-storey atrium, unique in Barcelona, to which the superior floors are poured to create a very complex space.
Most of the other floors of the building do not touch the entire perimeter of the tower and create a series of spaces of multiple heights perfectly visible from the street when you look at the tower in the backlight, an easy gesture to do if you look from the shadow it casts. In doing so, it is noticed that the interior and the exterior follow complementary but not coincident geometries that create a very rich play of light and shadow, translated in the interior in a very wide variety of spaces. On the third and fourth floors there is a complete auditorium, also noticeable on the façade, which reflects the versatility of spaces that the architect has managed to create in a plot and a volume as complex as those presented.
The tower has, in addition, some certainly interesting distant views that are worth discovering.

The ZeroZero Diagonal Tower is the latest addition to Barcelona's urban profile. Its position is exceptional: it is located near the sea, at the start of Diagonal Avenue, which is Barcelona’s main avenue. It is very visible from the city and from the coast, and it is located on the border between the consolidated city and the new large areas of public space in the Forum Zone.

The project takes this multiple condition as an opportunity to generate a contextual tower that is both a landmark and a public space, taking the alignments of the perimeter of the site as generators of the building. It is a sharp, stylised trapezoidal prism, a light, reverberating whitish construction. Its transparency reveals the dynamic and varied interior volumes that respond to the different specificities of the program and that are related to the various heights of the neighbouring buildings.

The external form responds to the city and the distant vision, and the internal forms to the functions and the closer vision, responding to the two simultaneous stairs that this type of building must solve. The ground floor follows the slope of the adjacent streets and is developed on three floors open to the public. This condition, which is extraordinary in a corporate building, where security is a critical issue, allows a direct relationship with the dynamics of the city, in a mutual benefit.

Within the volume of the building, four singular points are generated that enrich the whole and generate a varied experience of the interior: the atrium of the main lobby, 30m high and facing the Diagonal; an atrium on the 17th floor that reaches the crown of the building, facing the Maresme; the terrace and the double space of the Sala del Consell, located on the 23rd floor; and the auditorium for 350 people, which occupies two floors and is split into an auditorium and two amphitheatres that can be independent and operate independently for smaller groups, so that three events can be held simultaneously.

The office floors are open, taking advantage of the structural system adopted, a modified tube-in-tube scheme, with a central bearing core and a perimeter structure on the façade. This perimeter structure splits into two parts: very small and very slender inner pillars that only work in compression, and outer elements that solve the horizontal and torsional stresses. The slabs are 30 cm solid concrete slabs that transmit these horizontal stresses to the central core, forming a combined structural mechanism.

The struts form a rhomboidal framework in the façade that follows the static stresses of each part of the building, with a higher concentration of resistant elements in the lower parts and with a lower density in the upper parts. This framework creates a bright and changing presence on the outside, reinforcing the lightness of the tower and generating 4 different heights that change constantly depending on light and weather conditions.

The façade consists of a modular curtain wall with white aluminum profiles and extra-clear glass partially screen-printed with ceramic paint, following a vertical pattern that reinforces the slenderness of the building and contributes to its changing whitish image. In combination with the interior structure, arranged every 1.35 metres, and the exterior structure, this screen printing contributes to the diffusion of sunlight and the control of glare, generating interiors of high perceptual quality and remarkable visual comfort.

The main sustainability strategy of this building has been its austere design approach, driven by the need to meet a very tight budget. This condition has led to the search for the most efficient solution for each design problem, which has often meant choosing systems and materials for their ability to duplicate their function. Thus, the inner concrete core is uncoated and has the role of beautifully textured finishing material; exterior lattice is not only a key structural element, but also casts deep shadows on the façade by reducing solar radiation; screen printing on the curtain wall helps control sunlight and reduces maintenance needs due to its pattern, similar to saltwater tanks coming from the nearby sea; artificial lighting is also used as spectacular lighting for the simple design of two color temperatures of the lamps that differentiate the atriums from the other spaces in the tower. This approach has meant not only a substantial reduction in the number of materials used in construction, but has also allowed us to focus on the most important aspects of its construction and the clear and austere definition of its spaces.