Here's a link to an article with a little information about the Institut du Monde Arabe; the whole of the south-facing wall, shown here, is made up of panels which open and close (like the aperture in a camera) to regulate the light entering the building. We didn't go inside - but another time I'd certainly like to.
We stopped at a market at the end of Boulevard St. Germain on the way back, and got some tasty treats for our lunch; not just these, but some good bread too.
The building we were staying in was at the end of an L-shaped pedestrian road, with gates across each end. This shot, since it's wide-angle, looks rather odd but helps show how, even with no garden space, they still add some greenery in to the street.
And goodness - we must have walked A LOT on Saturday. Since it's still only lunchtime at this point, and we went out again in the afternoon, Day 3 is going to run to Part 4, rather than crowd more into this post.