The Centre of Pompidou, a daring architecture (both in style and in functionality) contrasting a lot with the old traditional surrounding Quartier de l'Horloge. The building construction ended in 1977 ( I remember being there that year) and hosts - amongst others - a very nice and important museum of modern arts (which I also visited in 1977, well ok I didnt enjoy it so much at that time but I wish I had time now to do it...)