to decorate hotels and railway stations defaced by Red Guards slogans. Zhou said that the artworks were for meant for foreigners, therefore were "outer" art not be under the obligations and restrictions placed on "inner" art meant for Chinese citizens. To him, landscape paintings should also not be considered one of the "Four Olds". However, Zhou was weakened by cancer, and in 1974, the Jiang Qing faction seized these and other paintings and mounted exhibitions in Beijing, Shanghai and other cities denouncing the artworks as "Black Paintings". Historical relics China's historical sites, artifacts and archives suffered devastating damage, as they were thought to be at the root of "old ways of thinking." Artifacts were seized, museums and private homes ransacked, and any item found that was thought to represent bourgeois or feudal ideas was destroyed. There are few records of exactly how much was destroyed—Western observers suggest that much of China's thousands of years of history was in effect destroyed, or, later, smuggled abroad for sale, during the short ten years of the Cultural Revolution. Chinese historians compare the cultural suppression during the Cultural Revolution to Qin Shihuang's great Confucian purge. Religious persecution intensified during this period, as a result of religion being viewed in opposition to Marxist–Leninist and Maoist thinking. Although being undertaken by some of the Revolution's enthusiastic followers, the destruction of historical relics was never formally sanctioned by the Communist Party, whose official policy was instead to protect such items. On May 14, 1967, the CCP central committee issued a document entitled Several suggestions for the protection of cultural relics and books during the Cultural Revolution. Nevertheless, enormous damage was inflicted on China's cultural heritage. For example, a survey in 1972 in Beijing of 18 key spots of cultural heritage, including the Temple of Heaven and Ming Tombs, showed extensive damage. Of the 80 cultural heritage sites in Beijing under municipal protection, 30 were destroyed, and of the 6,843 cultural sites under protection by Beijing government decision in 1958, 4,922 were damaged or destroyed. Numerous valuable old books, paintings, and other cultural relics were also burnt to ashes. Later archaeological excavation and preservation after the destructive period in the 1960s, however, were protected, and several significant discoveries, such as the Terracotta Army and the Mawangdui, occurred after the peak of the Revolution. Nevertheless, the most prominent symbol of academic research in archaeology, the journal Kaogu, did not