The pieces are printed on each side of thin foamboard, which you punch out of cards. There's also a card of printed acetate windows and double sided tape pieces for putting the windows in.
The puzzle/model starts by putting the west facade together. I was amazed by the number of pieces each step took.
The doors look so real, with a piece of foamboard for each layer of statuary. It looks amazing. And they got the pictures for the sculpture right - so each door has the proper tympanum and archivolts (sculpture above and around the door), rather than the same images printed 3 times. The rose windows are also different, though the other windows are copies of the same image.
Here's one side done, roof and all.
The finished cathedral looks incredible and is quite large. My cat walked around it while I was taking pictures, giving a sense of scale. Closed, it's over a foot high and at least a foot and a half long.
It even opens up so you can see the interior aisles and tiny altar.