Since 1969, this building has housed the collections of the library that dates back to the 15C, when the Dukes of Burgundy reigned over Belgium. It contains seven million books, including some magnificent pieces that can be consulted on site (most notably manuscripts and printed books). The building is also home to the Printing Museum and the Nassau Chapel. From mid-2020, the latter will house the new "Library of the Dukes of Burgundy" which will plunge visitors into the heart of European medieval culture.