#3 - Hang out around the Place de la Concorde, one of the major public squares in Paris. (Be careful crossing the street!)
Sandwiched between the Champs-Élysées to the west and the Jardin des Tuileries to the east, there is much to see here. The Obélisque de Louxor (Luxor Obelisk, pictured) stands at the center of the place, which is also home to La Madeline, the Hôtel de Crillon and the American Embassy. This is also where Queen Marie Antoinette and many others were beheaded during the French Revolution.
On the day we were there, we saw a rally for the rights of motorcyclists on the streets of Paris.