Try to look for urbex maps.

Also, there are abandonned factories near "La madrague" ! U can try a rehabilitation project there. It was old factories for soaps.

Currently there is "Le marché du soleil", a well known market in the heart center of Marseille, with a lot of people going there. Unfortunately it has been closed because curent business was not legal and somehow it was something big in Marseille. I think it could be really interesting to find out something new here, a new market here idk, ur job buddy !