Architecture was born to solve the problem of a roof, of something heavy and significant that accompanies and makes possible the human experience since ancient times. The floor may be the oldest architectural element, but the ceiling, due to the difficulty of its construction and the significance imposed by its permanence, requires an invention that goes beyond technique. Once the problem of weight has been solved, architecture, despite all the restrictions that have been imposed on it, becomes a victory; architecture has won because it has turned construction, all the difficulty and improbability of construction, into an art. What carries load, rests, what is weighted has become imponderable, the certainties are faced with a halo of uncertainty, the causality is put into crisis, and a suspension of meaning makes its way. From Greek to Gothic architecture, from Baroque architecture to the most admirable works and projects carried out by the pioneering architects of the Modern Movement, unusual examples arise. The expression of weight shows the various paths that challenge constructive practice and the imperative logic of gravity. And it is extraordinary that architecture, which does not have the same freedom as painting or sculpture, or literature or music, shows, within the same narrow margins that limit it, the value of the challenge it defies and the paradoxical freedom that belongs to it.