15th arrondissement
Most of what you'll run into here is from the 70's of this last century, which is why the place has gotten something of a reputation for being uncultured and ugly. If you have a soft spot for skyscrapers and the severity of glass and metal, though, this might be the perfect place for you. Otherwise, you might want to see what's going on at the local convention center, the Parc des Exposition.