We wandered around a bit too. This is one of the few 'passage ways' left in Paris. They're trying to revive them. Great to get out of the weather.
We also went to another area not really tourist friendly but if you want a little edginess in your life and to see a real diverse area then Saint Denis is a good place to go. Went by an Asian shop for some things, picked up coffee from a local roster, went to a Lebanese place for falafel and a bakery for a baguette. There's also Indian and vegan restaurants.
We know this place from our second trip to Paris when we lived in UK.
The archway is the entrance to the district.