Strasbourg, Luxembourg and Brusssels host various European institutions since the end of the World War II, each city having constructed dedicated buildings for them. Here, an architectural ambition has emerged that tries to face, not only the quantitative needs, but also the symbolic expression of these institutions. The architects aspired to produce an image both modern and solemn of these institutions within their different urban contexts. Thus, these buildings that draw upon the vocabulary of the modern movement, constitute the first symbols of Europe as well as the core of the urbanization of "European districts". This heritage, which is seemingly "paradoxical" in many respects, was approached in very different ways in the three sites: while it was valued and maintained in France, it was reinvented or erased in Luxembourg and Brussels. These processes have been fueled by Institutional developments, competition between states and cities for single-seat status, and the phenomenon of the "return to the city" of these neighborhoods that began in the 1980s. This contribution, based on archival research of the institutions and cities, analyzes the evolution—both architectural and urban— of the Europe’s first architectural symbols by highlighting the strengths and limitations of their heritage so as to shed light on the legacy that they have established over time. The evolution of the milestones of the three sites is discussed, revealing parallel logics but also a certain number of unique features.