Some windows at Chartres treated contemporary political subjects. The window of the emperor Charlemagne, donated by the furriers, subtly depicts the transfer of power from the East to the West. The emperor of Constantinople asks Charlemagne for help against the Muslim conquerors of the holy places. In return the Roman emperor offers Charlemagne holy relics, which he places on the altar of Aix-la-Chapelle. The narrative is an indirect reference to the 4th Crusade, contemporary with the building of the cathedral. Crusaders ventured to Constantinople indeed, although they plundered the city and took relics by force. In any case, the importance of relics couldn't be misunderstood in Chartres, where the already rich treasury was considerably augmented after 1204, among others with the heads of St. Anne and St. Matthew.
