Many of the original wall-paintings, dated to 1105/6, are preserved in the apse of the Holy Bema and the west wall of the church, which must have often suffered great damages especially from earthquakes. During the 14th century, for instance, the conch of the apse collapsed and was soon after rebuilt and redecorated. At the same time the external buttresses were added and a little later, the flying buttress at the eastern end of the north wall was built.