For 20 years now, Dominique Perrault have been working on the Great extension of the European Union Court of Justice. The initial Palace from the 70's was firstly extented by Pachovski and Frisch. This development is the consequence of the growing number of European communauties members from 15 to 28. This architectural complex is developed within a urban plan transforming the European quarter into a Luxembourg City district with streets, avenues and public spaces. Upon request of the Kirchberg Fund, Dominique Perrault designed a new urban fabric getting rid of the highway infrasctructures in order to create a "smooth soil", continuing the city-center public spaces. The third tower rises above the two others like a steeple. This is the finalization of the Galery, inner street and vertebral column of the building, creating thus a new eastern entry. Its architecture is influenced by the ring framing the original Palace and by the recent towers. It combines these two different architectures in order to create a kind of steel-like alloy, providing an aesthetical synthesis of the buildings of the Court. This new silhouette will appear in the Luxembourg landscape around Summer 2018.