During the 1980s, it was announced that Seville would host the forthcoming Seville Expo '92, to be held in 1992 to commemorate the 500th anniversary of Christopher Columbus reaching the Americas. To host such a large event, Seville needed to upgrade or construct an entirely new urban infrastructure. In response, Mayor del Valle launched the 1987 Plan General de Ordenación Urbana ("General Urban Planning Plan"), or PGOU, a type of urban plan, to modernize and re-draw the city's rail and road infrastructure. Del Valle's new plan replaced an older, outdated PGOU dating from 1964.