All the guidebooks will tell you to make a visit to Basilique Nortre-Dame de Montreal and if you're in Old Montreal, even if you do not walk inside you cannot avoid this edifice even if you wanted to. There is a small public square outside the gates and makes for a great stop to take a break and people watch. Visited during the evening with $10 admission fee (which includes the Light & Audio Show and self-tour). The Light Show was a bit cheesy but did give some good historical facts about the church and also allows you to appreciate the space, the architecture and the meaning behind the stain glass art.