"The west building is the most ornate in the Nunnery Court....Three principal planes of relief are established: the ground plane of latticed forms; the key frets of rectilinear units; and the rounded sculpture of serpent bodies and statues. A fourth plane is added by the over-door panels of serpent masks in tiers near the ends of the building. The effort to diversify the internal rhythms of the facade is not altogether successful, because the various combinations of forms are inadequately differentiated, and their scale does not command attention from a distance.
In the Governor's Palace, these timid and irresolute efforts received a much bolder restatement. Every corner is marked by a tier of five serpent masks. These are the only vertical arrangements: every other repetition of the serpent mask is diagonally staggered, so that an angular undulation of masks winds across the facades in five pyramidal outlines....Key frets, like angular eyes, mark still different diagonal rhythms in this system. What was a stiff grid of verticals and horizontals in the Nunnery, here resembles a supple basket weave of interlacing themes in distinct planes."
George Kubler, The Art and Architecture of Ancient America, p. 270