What is a common feature of Gothic cathedrals?

this is a experment where you actully have to do the work like go take some photos in something your interstid in

including the octave, the answer would 8 notes in a major scale with one note being played twice. ex) c major scale includes: c, d, e, f, g, a, b, c

notice that c is played twice

however, if you were to ask me how many different notes are in a major scale- the answer would be 7.  

prosumerism is the correct answer.