UNESCO has set itself the task of preserving those natural and cultural properties of the world that are of outstanding universal value. The international Convention of 16 November 1972 "Concerning the Protection of the World Cultural and Natural Heritage", the World Heritage Convention for short, is the most important international tool created by the community of nations to protect its cultural and natural heritage.
UNESCO's list of World Heritage properties comprises 1154 properties in 167 countries, of which 897 are cultural properties and 218 are natural properties. A further 39 sites on the UNESCO World Heritage List count as both cultural and natural heritage. There are also a number of cross-border World Heritage properties, such as the Monte San Giorgio, a site shared between Switzerland and Italy.
The cultural heritage properties currently on the World Heritage List include buildings of historic importance, town centres, archaeological sites, monuments to engineering history, industrial monuments and important memorial sites from human history.
Natural heritage includes important ecosystems, sites bearing witness to evolutionary history, natural paradises and conservation areas for plants and animals threatened with extinction.
A serial candidature is a nomination encompassing two or more non-adjacent areas. A single World Heritage candidature can consist of a series of cultural and/or natural objects in different geographical regions that belong to (i) the same historical or cultural group, (ii) the same type of object typical of a geographical zone; or (iii) the same geological or geomorphological formation, the same bio-geographical region or the same ecosystem. This category includes, among others, the "Prehistoric pile dwellings around the Alps".