I've come to realize that the best way to see a city is to run through it. Walking is fine, but you can only cover so much ground. Cars get you places, but you can't really see the scenes that well from inside, and the driver has to focus all attention on the road. Bikes aren't much better; pity the rubbernecking cyclo-tourist who gets doored while admiring the architecture. Bus tours are OK, but in the end I prefer to experience the city on my own terms, not in those of someone narrating the sights to me.
But, running you can see quite a lot in a short period of time. And it's easy enough to just stop if you want to spend a moment taking something in.
For instance, this morning I covered about 5 miles in about 45 minutes. On my run, I did a lap around the Jardin des Tuileries, passing by the Louvre, then up through the Place de la Concorde and onto the Champs-Elysees. At the top, I paused a bit to take in the Arc de Triomphe, then headed back home through the neighborhoods of the 8th arrondissement.
It's a lot to have seen before breakfast.
I've read that Paris is only 12K long. Perhaps I'll run the the length of the city later this week.