Look carefully at the photo above, what do you see? What questions would you like to ask?
How many of each coloured pane are there?
How would you describe the shape of the coloured panes of glass?
How big do you think this window is?
In how many different ways could you make a sensible estimate of its size?
Talk about the different options with someone else.
You may like to use whatever you like to make a drawing similar to what you see in the picture.