To be inscribed on the UNESCO World Heritage List, UNESCO World Heritage properties must be of Outstanding Universal Value and meet at least one of ten selection criteria. The Benedictine Convent St. John in Müstair meets criterium III for inscription.
Criterion (iii): The Benedictine Convent St. John in Müstair is one of the most coherent architectural works of the Carolingian period and High Middle Ages, with the most extensive cycle of known paintings for the first half of the 9th century. The Roman era's figurative paintings, especially the Carolingian period, are particularly important for understanding the evolution of certain iconographic Christian themes, such as the Last Judgement.
Integrity: The property comprises the entire monastic ensemble and the annexe elements for agricultural exploitation located within the walls of the ensemble. The property includes all the requisite elements to express its Outstanding Universal Value.
Authenticity: Historical and archaeological researches have determined all the restoration work in strict respect of the original substance since the 1947-1951 campaign. The property fulfils the conditions of authenticity not only with regard to the material substance but also from the functional perspective: the convent is still a religious centre for Benedictine sisters.
You can find further information at whc.unseco.org.