Franka Potente is to play the lead in Volker Schloendorff's adaptation of Donna Woolfolk Cross' best-selling novel Pope Joan, according to Production Weekly.

Potente will play Johanna von Ingelheim, a 9th century woman of English extraction born in the German city of Mainz who disguises herself as a man and rises through the Vatican ranks.

When her older brother dies in a Viking attack, the brilliant young Joan assumes his identity and enters a Benedictine monastery where, as Brother John Anglicus, she distinguishes herself as a scholar and healer. Eventually drawn to Rome, she soon becomes enmeshed in a dangerous mix of powerful passion and explosive politics that threatens her life even as it elevates her to the highest throne in the Western world.

Principal photography is expected to begin in May 2007.