On this side of the building (north side), a wide stair leads to the second level of structure IV, where the most important rooms are located. Doorways here open onto a wide terrace decorated with elaborate stucco work.
It appears that the two upper levels were only accessible from the other side of the building, either via the monumental staircase on the south or by a narrow interior winding staircase. There is no apparent stairway from Level 3 down to the lower north-side rooms.
The upper group of rooms at Levels 3 and 4 is therefore a truly self-contained unit, the function of which is unknown but hinted at by the arrangement of rooms at Level 4 around the residentially scaled courtyard. The seeming emphasis on good security and on restricted access to this unit suggests its use for elite residential purposes.