What are some good reasons for visiting the Cathedral of Notre Dame in Paris?

Notre Dame de Paris is considered by many people to be one of the finest examples of French Gothic architecture in the world. It also has many beautiful features, not the least of which are the famous stained-glass "rose windows," which were built in the 13th century. According to Wikipedia, The North and West windows still contain much original glass. I recommend visiting the Wikipedia cite for more architectural and historical information that would be of interest to a visitor and provides ample reason to go there should you have the opportunity to visit Paris.