Where: Bernburg, Germany Start of construction: 10th Century End of construction: 17th Century Most important renovation: 21st Century Accessible: yes, two museums, but due to renovation works they have been closed until the end of 2021. Important fact: current exterior dates largely from the 16th century. The round keep is the oldest surviving part of the original castle (12th century). http://www.museumschlossbernburg.de/