Sainte Chapelle is a tiny Gothic chapel located quite close to Notre Dame. You enter into the lower chapel (which is beautiful) where the "common people" worshiped, then climb a circular staircase to the main chapel. When you come out of the dark staircase into the chapel you are met with a thrilling burst of colors--the beautiful stained glass windows create a room full of jeweled light. It is an awesome experience to see these windows, each telling a biblical story, that ring the chapel. My husbasnd who originally came to St. Chapelle only because I wanted to, was fascinated by the beauty and craftmanship of the windows. Takes about 20 minutes to see (or you could spend hours gazing at the windows). A great experience (and free if you have the Paris Museum pass--as is Notre Dame, the Louvre and the Orsay).

The music was excellent, two performances in one night. If you wait for the second and pay between performances, the second one is half-price.
Tickets may be purchased at outlets in places such as FNAC. The audience is divided roughly into the front half and the back half, the latter seats being less expensive. There were only folding chairs, but one hardly notices. The staff is very friendly and helpful. I was embarrassed by an overbearing, obnoxious American man who was shouting at the usher because he, the American, had had difficulty finding his way in. The entrance was through the Conciergerie into the back entrance of La Chapelle. The chamber music was enchanting as we watched the sunlight filter through the stained glass windows. "Le Cygne" on the cello was my favorite while my husband's was "Meditation" from the opera "Thaïs." Afterward we watched one of the violinists put her instrument into a specially made backpack and bike off into the night.
Dress ranges from casual chic to elegant.

If you have time in Paris, I highly recommend stopping in to the amazing cathedral of Ste Chapelle. For a few Euros, you will be surrounded by the most extensive and amazing stained glass windows you have ever seen. You can sit and gaze upon them as long as you like and hopefully the sun will be shining to brilliantly illuminate them!