The Atelier de Moulage is a casting workshop in Brussels that was founded in 1876, back when similar casting houses were set up in Paris and London in an effort to bring sculpture to the masses. The original aim was to have copies of sculptural masterpieces available to the public.
The atelier is at the edge of the Parc du Cinquantenaire and is affiliated with the Musee Royal d'Art et d'Histoire, which is its neighbor. The atelier houses over 4000 molds which are (somewhat) organized and (definitely) numbered, as you will see in the photos below.
There is also a workshop full of the friendliest sculptors the world over. If you visit, they will invite you in, open up special rooms for you, and just let you hang out and take pictures.
I know there are lots of pictures here, but they really are remarkable. Thanks to B for taking most of them (the grainier iPhone pics at the end are mine).