Pyramid A1 is one of the principal structures of Group A, together with the ballcourt. The pyramid is high and measures at the base. It was built using cut stone and has four stepped levels, each of which terminates in a cornice. The pyramid faces west onto the plaza and has two access stairways with 27 steps each. The stairways are flanked by smooth balustrades built from well-fitted slabs. The summit of the pyramid supports a high platform that once formed the base for the summit temple. The pyramid was built over another structure, a stucco platform with two levels, the upper of which terminated in a cornice.