Complex sentence: The first industrial plant was the work of the French Darracq, who wanted to open a branch in Italy and chose a site for that purpose directly adjacent to areas which had hosted the 1906 International Exhibition in Milan.
Split into simpler sentences: The first industrial plant was founded by the French company Darracq, which had decided to open a branch in Italy. The site chosen for that purpose was directly adjacent to areas that had hosted the 1906 International Exhibition in Milan.