While touring around the Bulwarks at Old Fort Niagara North of Niagara Falls in Upstate NY, you can go into the ancient buildings that are just on the inside of the large earthen berms. Here we are inside the stone structure with wooden window frames and beams in the ceiling. The window was open in this dark building and provided the only light in the room. Note there are bars on the windows and very deep stone walls. THere are heavy inner wood shutters reinforced with metal too that can be closed in case of attack.