offering the aerial rights above Metro station entrances for construction through emphyteutic leases, an advantageous way to acquire prime real estate. When the Metro began running in 1966, ten buildings were already connected directly to Metro stations; development would continue until only three free-standing station entrances (Square-Victoria-OACI, St-Laurent and Place-des-Arts) remained in the central segment. In 1974, the Complexe Desjardins office tower complex was constructed, spurring the construction of a "second downtown" underground city segment between Place-des-Arts and Place-d'Armes station, via Place des Arts, Complexe Desjardins, the Complexe Guy Favreau federal government building, and the Palais des Congrès (convention centre). Between 1984 and 1992, the underground city expanded, with the construction of three major linked shopping centres in the Peel and McGill Metro station areas: Cours Mont-Royal, Place Montréal-Trust, and the Promenades Cathédrale (built underneath Christ Church Cathedral). McGill station was already linked with The Bay, Eaton's (now the Complexe Les Ailes), Centre Eaton, and two other office/mall complexes. Between 1984 and 1989, the underground city grew from of passages to almost . Mega-projects added to the size of the network throughout the 1990s, including Le 1000 De La Gauchetière (the tallest building in Montreal), Le 1250 René-Lévesque, and the Montreal World Trade Centre. Although these buildings have only a secondary commercial sector, they use their connection to the underground city as a selling point for their office space. Also, the construction of a tunnel between Eaton Centre and Place Ville-Marie consolidated the two central halves of the underground city. The construction of the Bell (originally Molson) Centre connected Lucien-L'Allier Metro station to the underground city, as well as replacing Windsor Station with the new Gare Lucien-L'Allier commuter train station. Most recently, in 2003, the complete redevelopment of the Quartier international de Montréal consolidated several segments of the central underground city with continuous pedestrian corridors. The construction of the ICAO headquarters joined Place Bonaventure to Square-Victoria-OACI station, which in turn was joined to the Palais des Congrès and Place-d'Armes station via the new Caisse de dépôt et de placement building and a tunnel under Place Jean-Paul Riopelle. Uniquely, the new tunnel sections in the Quartier International contain educational and artistic displays sponsored by major Montreal museums. As a result of this construction, one can now walk all the way across the centre of downtown, from the UQAM Sherbrooke Pavilion at the corner of Sainte Famille Street and Sherbrooke Street to