Sideco) in 1972. The Conurban Tower was inaugurated in 1973, Carlos Pellegrini in 1974, and Catalinas Norte, in 1975. Work then began on the Madero Tower (so named for its Eduardo Madero Avenue address) in 1976, and in 1979, the IBM Tower. These high rises, while not the first in Buenos Aires to incorporate elements of the International Style (such as curtain walls), became the first to do so as a group. SEPRA Arquitectos, a prominent Argentine architectural firm, designed the Sheraton Hotel and the Catalinas Norte Tower. The implosion of the dictatorship's economic policies in 1981 led to a suspension in new developments for the area, however, as well as a sharp decline in new construction as a whole. A subsequent economic recovery that followed Economy Minister Domingo Cavallo's 1991 Convertibility Plan prompted renewed interest among developers, and from 1995 to 1998, the Consultatio Group developed the Alem and Catalinas Plaza twin towers, and IRSA, Laminar Plaza (all designed by SEPRA). The final addition to the complex during the 1990s was the Bank Boston Tower. The Postmodern high rise, designed by César Pelli, was completed in 2001 and at 137 meters (450 ft), would become the tallest in the district. Expansion to the south The flurry of new construction also led to the redevelopment of the southern end of MCBA's redevelopment district (located in the San Nicolás ward). The Bouchard Tower and Loma Negra's Fortabat Tower, both designed by SEPRA, were built between 1991 and 1995. The República Building, designed by Pelli for the now defunct Banco República, was completed in 1996 (with Telefónica de Argentina as its chief tenant). The Microsoft Building (by Mario Roberto Álvarez), opened in 2001, and Bouchard Plaza, designed by Hellmuth, Obata and Kassabaum for the La Nación news and publishing group, opened in 2004. Sale of last remaining lots The complex, which by 2004 included 15 buildings totalling over 540,000 m² (5.8 million ft²), was in the news during 2009 and 2010, when Mayor Mauricio Macri obtained the City Legislature's approval to sell the remaining three undeveloped lots. The combined land is zoned to house up to 120,000 m² (1.3 million ft²) of new office space, and the city sanctioned the future construction of high rises of up to 50 stories, and 150 m (492 ft) in height (slightly more than the tallest building currently in Catalinas). The third and last lot was