While I was in France this weekend, I wanted to compare French traditions to those of the Romans. Right away I learned that long meals also take place in Paris. Be prepared to wait an hour and a half for your food in a nicer restaurant. At least while you wait in Paris you get free bread and water! Make sure to take advantage of this while it lasts.
Another commonality between the two cities is how they socialize and use outside spaces. While Paris does not have piazzas like Rome, they do have the lawn in front of the Eiffel Tower. Make sure you put it on your to-do list to visit here after dark. Bring a bottle of wine and some bread with you when you go. You will hear music and continually have to turn street vendors away, just like in a Roman piazza. And every hour on the hour, you will get a free light show as thousands of lights flash on and off up and down the tower. It is an event you should make a priority when in Paris.