The present work is devoted to a significant period of medieval history of Tibet, during a crucial spell when the noble house of the Phag mo gru pa dominated Central Tibet. On the basis of a great variety of Tibetan sources, this present study investigates the entire period from the mythical beginnings of the Rlangs Phag mo gru pa clan until the end when the noble house played no political role anymore. Maintaining a strictly chronological approach, a comprehensive study of the political and historical activity of the noble house from the 12th to the 17th century is offered. A particular focus will be placed on the period of the 14th century which saw the rise of this noble house as ruler of Central Tibet. It can be argued that the Rlangs Phag mo gru pa were a defining factor in Tibetan politics from the middle of the 14th century to the mid-16th century. The second part of this publication is devoted to a detailed study of the architectural history and the religious art of Gdan sa mthil monastery. It was famous for its commemorative stupas that were adorned with a variety of reliefs and statues of which a part has survived. By investigating and evaluating a number of Tibetan inventory texts and a number of historical photographs, an attempt has been made to reconstruct the full range of figures found on these commemorative stupas iconographically. The book is lavishly illustrated with 48 drawings and 415 plates. This study is also of great importance for museums, auction houses and art collectors. The work is finally supplemented with nine appendices on the succession of the abbots and throne holders of the Phag mo gru pa, on further noble houses and so on.