Le Corbusier's Notre-Dame du Haut (the Ronchamp Chapel) is a deliberate abandonment of everything the same architect argued for twenty years earlier — the right angle, pilotis, thin white prisms, the machine aesthetic. Here Corbusier leaves the rational box and moulds concrete like a sculptor; architecture passes from calculation to emotion.

The building contains almost no straight line: the walls curve and thicken downward, one bowing inward and up; the heavy, dark concrete roof sags down over the walls like a sail or a mushroom. The roof does not in fact rest fully on the wall — light seeping through a thin gap left between them makes the vast concrete mass seem to float. The south wall is over a metre thick and is pierced with windows scattered irregularly, funnel-shaped in depth, small outside and large within; the coloured light from each scatters inside the thick wall to form floating patches of light in the dim interior.

At Ronchamp structure and form derive not from function but from the spiritual effect to be made by light and space. Le Corbusier turns concrete — the rational material of modernism — into a wholly plastic, almost primal means of expression. The chapel is a turning point showing that modern architecture is not only cold geometry, that concrete too can produce an emotional, sculptural architecture carved by light; it is the source of a line running from brutalism to contemporary 'phenomenological' architecture.