In addition to the wealth generated by customs duties and Argentine foreign trade in general, as well as the existence of fertile pampas, railroad development in the second half of the 19th century increased the economic power of Buenos Aires as raw materials flowed into its factories. A leading destination for immigrants from Europe, particularly Italy and Spain, from 1880 to 1930, Buenos Aires became a multicultural city that ranked itself alongside the major European capitals. During this time, the Colón Theater became one of the world's top opera venues, and the city became the regional capital of radio, television, cinema, and theater. The city's main avenues were built during those years, and the dawn of the 20th century saw the construction of South America's tallest buildings and its first underground system. A second construction boom, from 1945 to 1980, reshaped downtown and much of the city. Construction of the Obelisk of Buenos Aires on the 9 de Julio Avenue, 1936. 9 de Julio Avenue, 1986.