Caracas grew in size, population, and economic importance during Venezuela's oil boom in the early 20th century. In the 1950s, the metropolitan area of Gran Caracas was developed, and the city began an intensive modernization program, funding public buildings, which continued throughout the 1960s and early 1970s. Cultural landmarks, like the University City of Caracas, designed by modernist architect Carlos Raúl Villanueva and declared a World Heritage Site by UNESCO in 2000; the Caracas Museum of Contemporary Art; and the Teresa Carreño Cultural Complex were built, as well as the Caracas Metro and a developed downtown area. Urban development was rapid, leading to the growth of slums on the hillsides surrounding the new city. Much of the city development also fell into disrepair come the end of the 20th century, with the 1980s oil glut and political instability like the Caracazo, meaning maintenance can not be sustained. The economic and social problems persist throughout the capital and country, characterized as the Crisis in Venezuela. By 2017, Caracas was the most violent city in the world.