If you go to St. Chapelle, hold on to your ticket. You can get a two Euro reduction on your Seine River boat ride (with Vedettes de Pont Neuf, Metro: Pont Neuf). The boat ride costs 10 Euros, but I really like this particular launch site at the Vert Galant Park at the tip of Ile de la Cite (just a short walk from St. Chapelle located in the Palais de Justice on Ile de la Cite.
We left on the 6 :30 pm launch and the boat was almost empty in the front seats. Behind us, sat two Parisians who were enjoying the trip as much as we were (until the rain came!) but there is covered space for a hasty retreat. The commentator is a real live person with a delightful touch of an accent – who actually encourages you to ask questions during the trip. Go and say hello to her at the end of the trip and express your appreciation.