As you visit each of the links for the listed cathedrals, take thorough notes of the elements of these Gothic buildings and how each cathedral uses these elements to construct a church that is unique to their town. As you view the sites, you will notice how even though each of the cathedrals are Gothic in style, they each have their own unique style and characteristics.
Gothic Architecture Background - http://www.abelard.org/france/cathedral-construction.php
Westminster Abbey - http://www.westminster-abbey.org/home
Milan Cathedral - http://www.milano24ore.net/cityinfo/tour/cathedral/
Chartres Cathedral - http://www.sacred-destinations.com/france/chartres-cathedral
Notre Dame de Paris - http://www.notredamedeparis.fr/-English-
Amiens Cathedral - http://www.sacred-destinations.com/france/amiens-cathedral