The jewel in the museum's crown, however, is undoubtedly the gleaming mahogany Wallenrodt Library, which was founded by Prussian Chancellor Martin von Wallenrodt in 1623 based on his own private collection. In spite of its secular nature, it was relocated to the cathedral by his son in 1650 and was then by various means built up to a collection of over 10,000 books and manuscripts. Badly damaged with the cathedral in WW2, it was only restored to its former glory in 2005.