In the center of the building, Gaudí expanded the existing patio and installed a large skylight. He placed the elevator shaft and stairwell inside here, while incorporating a way to distribute light evenly through the building.The patio walls of the upper floors are covered by cobalt-blue tiles; proceeding downwards, the color of the tiles fades to white. The darker tiles, which are closer to the skylight, reflect less light; the white tiles reflect more. When viewed from below, the patio walls look to be a continuous blue color. Gaudí placed smaller windows on the upper floors of the patio and larger ones on the lower levels in order to ensure an even amount of light to flow inside.