This building was used as the offices of the Expo 2008. Subsequently, it will be used as the seat of the United Nations during the 'Decade of Water 2005-2015'. The assembling of the volumes set out in the Metropolitan Water Park project is created by the complementary relationship between the two prismatic volumes of the building, with the volume corresponding to the ground floor establishing the closest relationship to the avenue. The entrance appears as an insert in the encircling glass wall, where a clearly horizontal proportion emerges above a covered garden area; this covering is intended to encourage the use of the area. The orientation of the volume of the ground floor (the most public of the zones in the building), gently slides towards the east of the volume's four floors with its central core. A flexible organization of the different floors and its later 'compartmentalization' is thereby allowed.