When designing the building Nouvel aimed to reject the prevailing conception of a skyscraper. As a result the building is not only nice but also "smart": the facade consists of two layers. The inner one is made of concrete and is covered with colorful metallic blades. The outer one looks like multicolored jalousie. This mechanism simplifies the ventilation system: in winter it preserves hot air within the building, and in summer it distributes the cold air inside. The grand opening ceremony took place on September 16, 2005; king of Spain honored the event with his appearance.

In his interviews Nouvel used to tell that he was inspired by the Montserrat Mountain that "rose like a fountain from the depths of earth". During sunny hours the tower resembles a huge fountain, splashes of which play like a rainbow.

Owing to its shape Agbar was nominated for "Catalog" magazine awards of most phallic buildings around the world. However it failed: the prize went to another phallic art work - Ypsilanti water tower. It’s quite fair, as Agbar is more like a cigar than a phallus. Anyway human imagination is boundless and sometimes Nouvel himself described Agbar as having a phallic shape.

The building is "covered" with 4000 colored lamps that create illumination of 16 million color tints. Owing to this beauty thousands of tourists and locals gather here at New Year Eve, and Barcelona is broadcasted all around the world along with Sydney, New York, Paris and London.