The United Nations Educational, Scientific and Cultural Organization (UNESCO) World Heritage Sites are places of importance to cultural or natural heritage as described in the UNESCO World Heritage Convention, established in 1972. Cultural heritage consists of monuments (such as architectural works, monumental sculptures, or inscriptions), groups of buildings, and sites (including archaeological sites). Natural features (consisting of physical and biological formations), geological and physiographical formations (including habitats of threatened species of animals and plants), and natural sites which are important from the point of view of science, conservation or natural beauty, are defined as natural heritage. Spain ratified the convention on May 4, 1982, making its historical sites eligible for inclusion on the list.
Spain has 50 sites on the list, which is the fifth largest number of sites per country, behind Italy (62), China (61), France (56), and Germany (55). In addition, Spain has 35 sites on its tentative list. Sites in Spain were first inscribed on the list at the 8th Session of the World Heritage Committee, held in Buenos Aires, Argentina in 1984. At that session, five sites were added: the Cathedral of Our Lady of the Assumption, Córdoba; The Alhambra and the Generalife, Granada; Burgos Cathedral; Monastery and Site of the Escorial, Madrid; and Park Güell, Palau Güell and Casa Milà, in Barcelona. Five sites were added in 1985, and another four in 1986. Apart from 1984, 1985, and 1986 (Spain's first three years as a member), 2000 saw the most new sites inscribed, with five that year.
Of Spain's 50 sites, 44 are cultural, 4 are natural, and 2 are mixed (meeting both cultural and natural criteria). Three sites are located in the Balearic Islands and four are in the Canary Islands. Four sites are transnational. The Pirineos – Monte Perdido World Heritage Site is shared with France, the Prehistoric Rock-Art Sites in the Côa Valley and Siega Verde site is shared with Portugal, Almadén is listed alongside Idrija in Slovenia and the Ancient and Primeval Beech Forests of the Carpathians and Other Regions of Europe are shared with 17 other European countries.
World Heritage Sites UNESCO lists sites under ten criteria; each entry must meet at least one of the criteria. Criteria i through vi are cultural, and vii through x are natural.