The Obelisco de Buenos Aires (Obelisk of Buenos Aires) is a national historic monument and icon of Buenos Aires. Located in the Plaza de la República in the intersection of avenues Corrientes and 9 de Julio, it was erected in 1936 to commemorate the quadricentennial of the first foundation of the city.Construction began on March 20, 1936, and it was finished on May 23 of the same year. It was designed by architect Alberto Prebisch (one of the main architects of the Argentine modernism who also designed the Teatro Gran Rex, in Corrientes and Suipacha) at the request of the mayor Mariano de Vedia y Mitre (appointed by president Agustín Pedro Justo). For its construction, which cost 200,000 pesos moneda nacional, 680 cubic meters (24,000 cu ft) of concrete and 1,360 square meters (14,600 sq ft) of Olaen white stone from Córdoba were used. The obelisk was built by the German company G.E.O.P.E. - Siemens Bauunion - Grün & Bilfinger, which completed its work in a record time of 31 days, with 157 workers. The rapid hardening Incor cement was used and was built in sections of 2 meters (6 ft 7 in) to facilitate the dumping of concrete. Its height is 67.5 metres (221 ft), and 63 metres (207 ft) of these are up to the initiation of the apex, which is 3.5 by 3.5 meters (11 by 11 ft). The tip is blunt, measuring 40 centimeters (16 in) and ends in a lightning rod that cannot be seen because of the height; its cables run through the interior of the obelisk. It has only one entrance (on its west side) and on its top there are four windows, that can only be reached by a straight staircase of 206 steps with 7 breaks every 6–8 meters (20–26 ft).