The Commissariat Building, also known as the Bytown Museum, is an imposing three-storey, rough-coursed masonry structure that features three bays, a gable roof, supply doors on all three levels of the building, and a regular fenestration pattern. The Commissariat Building is located on the west side of the locks at the Ottawa Lockstation, at the lower end of Colonel By Valley, in the heart of Ottawa. As part of the Rideau Canal National Historic Site of Canada, it is the northernmost station along the Rideau Canal and is the oldest remaining stone building in Ottawa.