La Sainte Chapelle
This might just be the most beautiful church in Paris. A masterpiece of Rayonnant Gothic architecture, La Sainte-Chapelle boasts one of the world’s most complete and stunning sets of 13th-century stained glass. With a ray of sunlight, the upper chapel fills with a kaleidoscope of colors. This spectacular spot is no secret and there’s often a long line to enter. Visit during the work week if you can and purchase your ticket online ahead of time. If you’re planning to visit the Conciergerie next door, buy a joint Conciergerie + Sainte Chapelle ticket and visit the Conciergerie first to skip the long line outside the Sainte-Chapelle.