This year marks the 40th anniversary of the World Heritage Convention, one of UNESCO's most successful programmes and one of the most powerful tools for heritage preservation. Almost universally adopted, with 188 signatory countries, the Convention is unique in that it combines the protection of cultural and natural heritage in one instrument. Since its adoption by the General Conference of UNESCO in 1972, the World Heritage List has grown to include 936 sites inscribed for their outstanding universal value in 153 countries around the world.