Casa Batlló (Photo 4 of 9)
The first floor window on the left hand side, which you can clearly see in this shot, was a design room used by the owner of this building. Gaudí designed this room to accurately control the amount of light that could enter the room through an elaborate shutter mechanism on the inside. The windows are so large that too much light would have entered the office and so Gaudí incorporated stained glass in the upper half of the window to soften the light and reduce the light intensity.
The windows were designed to open fully if required giving the occupants an almost un-obscured view of the street.