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In page Charlemagne:

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He was buried that same day, in Aachen Cathedral, although the cold weather and the nature of his illness made such a hurried burial unnecessary. The earliest surviving planctus, the Planctus de obitu Karoli, was composed by a monk of Bobbio, which he had patronised.[2] A later story, told by Otho of Lomello, Count of the Palace at Aachen in the time of Emperor Otto III, would claim that he and Otto had discovered Charlemagne's tomb: Charlemagne, they claimed, was seated upon a throne, wearing a crown and holding a sceptre, his flesh almost entirely incorrupt. In 1165, Emperor Frederick I re-opened the tomb again and placed the emperor in a sarcophagus beneath the floor of the cathedral.[3] In 1215 Emperor Frederick II re-interred him in a casket made of gold and silver.