We also thought we might be able to do Euro 14.00 cheaper at a hotel right next door and therefore packed up. We later brought the bags there at only 9:00 am. We left them downstairs as the room wasn't guaranteed to be free until 2:00 pm.
We initially thought we'd do a tourist bus to get our general orientation. Then after waiting we decided to check to see if Metro had tourist fares. We instead got 3-day unlimited passes for 18 Euros. We tried them out by going to the Eiffel Tower. What fantastic weather! We couldn't have ordered it any better.
Later in the afternoon we went back to Notre Dame by subway. One final trip was out to Place de Clichy. Wouldn't you know, there really is a Moulin Rouge!