"Structure X, which bounds the west end of the great central plaza. has lateral wings that consist of lower structures, each surrounding a courtyard. From the shape of the debris, these can be presumed to consist of a single level of rooms.
The relief sculpture on the center unit of the upper, east facade is of stone covered with plaster, and painted a dominant red plus gold and blue-green. The only special features observed at Str. X. are small openings in the front upper façade. Ruppert labled them ventilators, but they are so small that neither ventilator nor window seems an entirely appropriate designation. The largest measures about 15 by 19 cm and opens through a wall approximating 1 m in thickness. Penetrating the sculptured portion of the east facade or the wall immediately adjacent to it, they might be interpreted as observation portals, except that the view from them is so constricted that essentially only Structure VIII, not the plaza below, can be seen." (Potter 1977:56-61)