The Acropolis of Athens or Citadel of Athens is the best known acropolis (Gr. akros, akron, edge, extremity + polis, city, pl. acropoleis) in the world. Although there are many other acropoleis in Greece, the significance of the Acropolis of Athens is such that it is commonly known as The Acropolis without qualification. The Acropolis was formally proclaimed as the preeminent monument on the European Cultural Heritage list of monuments on 26 March 2007. The Acropolis is a flat-topped rock that rises 150 m (490 ft) above sea level in the city of Athens, with a surface area of about 3 hectares. It was also known as Cecropia, after the legendary serpent-man, Cecrops, the first Athenian king.