If you approach Renzo Piano's Paris office from the Seine, it looks like just another bourgeois entrance - simple name-plate, passage, bell, metal door. If you approach it from the north, though, you immediately see why the sign reads not "Renzo Piano Architect" but "Renzo Piano Building Workshop".

The lofty model shop acts as a storefront, one that evokes the city of craftsmen that Paris once was, with its exquisite miniature buildings emerging from piles of card and timber, walls of beautifully arranged tools and projections of huge new pieces of cities around the world. Among the neutral colours, a few flashes of fruity shades twinkle: bright red, fiery orange, lemon yellow, lime green.