The Forge was built away from the religious buildings of the monastery, so as to mark a clear separation between prayer and work, which were the two main activities of the monks. It dates from the late 12th century. This building, which measures more than 50 meters long, is reinforced by a series of powerful buttresses that evoke intense activity.
Archaeologists who have studied the Forge and iron mines nearby believe it is one of the oldest metallurgical plants in Europe. It probably had two furnaces and several mills operating hydraulic hammers, one of which was recently reconstituted.
The sale of the production at the Forge procured substantial financial resources to the Abbey.