Cesare Borgia is imprisoned for refusing to surrender the castles
he had conquered in the Romagna to the new Pope Julius II. Once he
has given up these possessions, he is freed again.
Citation:
Editors. "Cesare Borgia is imprisoned for refusing to submit to the new Pope".
The Literary Encyclopedia. First published 01 November 2010
[http://www.litencyc.com/php/stopics.php?rec=true&UID=14080, accessed 19 May 2013.]