For a time it was attributed the function of market by the presence of low platforms; however, the most recent explorations refer that these buildings were decapitated and that it was not its original form. The importance of this Acropolis lies in the presence of an exquisite mural painting. Group A is an elongated basement containing not very tall buildings that delimits the complex to the south, as if it were a portico. In an earlier construction stage, mural painting was identified on an elongated sidewalk that overlooks the outside of the complex. In this painting aquatic motifs can be observed, as well as the Chiik Nahb glyph, which gives its name to the Acropolis.

The main and tallest building of this Acropolis, Structure I, oriented towards the south, is located in Group I and shelters in its interior the Substructure Sub I-A. The latter is radial in shape, profusely decorated with murals depicting richly attired people participating in some social event. The structure was arranged to be observed from all angles of the Acropolis. To the south of this structure is located a small plaza of the Slab of Mythological Beings, a rocky outcrop that has three mythical characters sculpted on it. The other groups show apparently decapitated structures, except for groups J and K, which are not explored. The latter delimits the Acropolis to the west and is perhaps the most elongated structure in the entire city.

It shows two successive architectural phases that correspond to the transition between two critical periods of the history of Calakmul; it presents a remodeling, around the year 672, which probably coincides with the death of the characters buried in the three burial chambers found in this building, one of them is the one that appears represented and named in Stela 79 and that could be the mother of the ruler Garra de Jaguar, who ruled Calakmul from the year 649 to the beginning of the years 700 AD.