these mounds, which are nearly flat, are some 13 feet above this level.
The sides of the mounds slope very sharply, and have suffered somewhat
from erosion, being cut by deep gullies, as shown in figure 328, which
is an enlargement from the map. It has been stated that these structures
were mounds, pure and simple, used for sacrifice or worship, resembling
somewhat the well-known pyramid of Cholula; but there is no doubt that
they are the remains of house-structures, for a careful examination of
the surface on the slopes, reveals the ends of regular walls. The height
is not exceptional, the mound on the east being less than 3 feet lower,
while the one on the southeast lacks less than 4 feet of its height. The
characteristic feature, however, and one difficult to explain, except on
the hypothesis stated, is the sharp slope of the sides. It will be
noticed that the raised base or terrace on which the mounds are located
is not perfectly flat, but on the contrary has a raised rim. This rim
seems quite inconsistent with the theory which has been advanced that
the terrace was built up solidly as a terrace or base, as in that case
it would seem natural that the slope from the base of the mounds to the
edge of the terrace would be continuous.

There is an abundance of room between the crest of the rim and the base
of the terrace for a row of single rooms, inclosing a court within which
the main structures stood, or such a court may have been covered, wholly
or partly with clusters of rooms, single storied outside, but rising in
the center, in two main clusters, three or more stories high. Such an
agglomeration of rooms might under certain conditions produce the result
seen here, although a circumscribing heavy wall, occupying the position
of the crest of the rim and inclosing two main clusters each rising
three or more stories, might also produce this result. The difficulty
with the latter hypothesis is, however, that under it we should expect
to find a greater depression between the base of the mounds and the edge