Holes in walls and what's with those windows?
Have you noticed places in the wall where a brick seems to be missing? These putlog holes will hold the ends of timbers needed to support the scaffolding. Spaces in the window frames have been left for the insertion of metal rods, which will help support the heavy glass and lead windows.
The flared frames of the chapels windows aren’t a mistake! That splay is intentional. This design, seen in many historical structures, channels more light inside.