Why don't tap the sun in summer and the ventilation in winter? A solar greenhouse could ease the natural ventilation when the hot sun heats the air up, it goes up and, at the same time, the cool air comes inside from below. During the winter a forced ventilation could be improved thank's to the same solar greenhouse because the air inside it will be always warmer than the outside one and the issue will be the energy saving.A new stair in front of the square breaks the front's symmetry and static shape and hosts two sliding scales. The stair could be the new VIP entrance during expo as well.