The Bourse de Commerce holds a bare concrete cylinder inside a domed grain market, with a walkable gap running between them. Stand under the dome and you see two buildings at once. A painted band runs right round the base of the glass, 1,400 square metres of ships, ports and cargo across five continents, ten metres deep on its own. The dome peaks about forty metres above the floor. Inside the ring stands Tadao Ando's concrete wall, nine metres high and twenty-nine across, smooth and bare.
The hall was built to keep the price of bread steady. Paris traded and stored its grain here, in a ring of covered galleries around an open yard, and roofed that yard with a wooden dome which later burned down. Iron replaced it, then glass. When the building became a commodity exchange the painted band went up around the rotunda — look up and it is still there, running the whole way round above your head. Grain, sugar and coffee were dealt under it until the last market closed. Ando's concrete wall arrived a generation after that, and the art shown inside it changes completely between exhibitions.