On my way to St Lawrence Market, I stopped by this Cathedral. From the outside, the cathedral is big and with a gothic architectural design. When you walk in, you are greeted with an absolutely gorgeous stained glass church. It's open to the public. So go inside, take some pictures, and enjoy the good vibe. Treat this place like a library. The tourists try to stay quiet as possible or speak in low voice. They do have services here on Sunday morning. If you are not interested in attending the church service, I recommend going in the afternoon on Sundays.